Hi Gary [is it?] and welcome to the forum.
As you no doubt appreciate with the questions you have emigrating can be complex enough without the added complexity of a family and future education issues.
Unfortunately, it just got a bit more complex with the government announcing yesterday long awaited changes.

Just a bit of background to that and as a result of the global economic issues and Australia not totally removed from that, 2009 was a year for some significant progressive changes and we ended up with an immigration prioritisation approach coupled with a Critical Skills List [ CSL ]on top of other listings - http://www.immi.gov.au/skilled/gener...processing.pdf the good news there for you is that Aircraft Maintenance Engineer - Avionics is on the CSL

2009 was also a year where some focus was put on exponentially increasing international student numbers, many having worked out with help of recruiting agents overseas that this was an easy ticket for permanent residency and because it was too easy and recognised for that there has been some abuse of the process, that bringing the focus and further subsequent changes, comment and links on
DIAC New GSM Plan/Priorities

One of the key areas addressed was what was called MODL, a demand occupation list between the more standard SOL and the CSL and MODL had additional points available for occupations on the list including some that became the international students easy road.
MODL has been revoked and though that along with other changes may put something of a road block on the easy road it is also unfortunately going to affect occupations on the CSL.

So that's the background and against that, comments on your questions:

First, re the processes for immigration and the new priority approach will have Employer Sponsorship at the top still followed by applicants with a nomination by a state where their occupation is to be on a new state immigration plan as approved by the Federal Immigration Minister and we may not see those for at least a couple of months so other than the ES approach I'd hold on any moves too quick.

The very first thing most people need to do for immigration is to have their qualifications assessed and as you'll likely be in a better position with Avionics I would look at having that done, details of assessing authority will be on the SOL, a listing at rear or via A-Z Occupations List - Australian Skills Recognition Information .
Though a new SOL is to be developed, the old one can still be accessed via Professionals and other Skilled Migrants - Workers - Visas & Immigration and from that page you can also access the What's New various links or take the Visa Options on to Skilled GSM 175/176 visas where under eligibility sections you'll find self assessment tables though they may now be out of date if MODL is still showing.

One thing you should note on a self assessment table is that 12 months experience in the past 24 is a mandatory immigration requirement for the 175/176 and hopefully your PM work has kept you sufficiently connected with the Avionics side of things.

A read of a whole visa, the 175 or 176 will give you a good understanding of the system - a bit like a project you could say.

And so!
1. There's no set funding re skilled immigration applicants though some states may have a recommended or required ammount on their state nomination sites [ links from the 176 visa eligibility section ] though not all that much I believe and possibly about the ammount you may want to have to cover your family living costs for a few months or however long you might think it could be before you find work.
I've read of some families coming out with just $10,000 to back them but personally I'd want to have a bit more for security sake - no Social security entitlements for first two years.

2. & 3.
Primary - years 1-6 , ages 5/6 to 11/12
[There is talk of making year 1 at secondary into a Primary year 7.]
Secondary years 1-6 or as it is commonly referred to 7 - 12
ages 11/12 - 17/18 and then University or alternative courses.

I assume your GCSE is like a final secondary school certificate, the testing level for University entrance.
In Australia, education has been a state by state governed sector though there is more and more rationalisation, Australian school system* perhaps being a relevant site.
Final secondary school level in the past been called things like Matriculation or just HSE or HSC.

4. I take it from if you mean in relation to immigration agents, whilst there are certainly lesser quality agents about just as you can find in any field and they will likely be tested with new changes, there're also quality agents who'll not be in the practice of making false claims I'd hope but at the same time you need to realise they have no magic wands to wave and they'll have clients in limbo a bit while there're regulations being finalised.

As I've said above, other than the ES approach and getting your qualifications assessed it is probably worth waiting until the new situation gets fully established, a good time for you to make yourself familiar with various visa options, read the eligibility requirements and study the Applying for Visa sections, they having a good Checklist and then there're Booklets #5 & #6 though recognising that there'll be some things to be affected by the changes announced.

That exercise will enable you to both assess whether you think you can do your own application [and many do - more than 50%] or just build your own knowledge to help in the selection of an Immigration Agent.

5. We have in Australia Medicare which is a partial NHS providing for access to public hospital treatment, discounted medicines and rebates on Doctors and other medical fees.
In addition there are various levels of private insurance for private hospital coverage and miscellaneous medical treatments.
Private Health Insurance Australia - iSelect will allow you to have a look at different funds.

6. & 7. Four major banks here, ANZ, Commonwealth, National and Westpac and a few what we call seond tier and a lot of them allow for accounts to be opened from abroad and you can transfer money in so it's here when you arrive - ANZ - Travel and foreign exchange - Foreign Currency Rates & Currency Converter
being one.
Not too sure on how banks go about sorting out credit ratings for immigrants but can't be too big a deal as hundreds of thousands of immigrants over the years have bought property etc.

The Department of Immigration & Citizenship "Living In Australia " section from header bar has a lot of good links for general stuff and worth a read.

The Emigration fair could give you some info though no idea on who they get there.
Welcome to Hire A Migrant and Jamie is an employment agent who may be worth contacting for he is one that also keeps abreast of immigration regulations.

If you have a month off, I'd do a quick google - for instance: Google for instance and shoot out some emails with a CV and see what responses you get back.

Get anything that looks and you might want to arrange a quick recce trip like some do, getting an ETA Business - Electronic Travel Authority (ETA) - Online Applications can be done online with more or less instant grant.
Welcome to AirAsia.com, The World's Best Low-Cost Airline ex Stansted > KL > Oz can be good for cheap flights if major airlines are too expensive when booking close to flight date.

Getting qualifications approved can take a while and depending on how soon you leave the military, you may be able to start on an ES temporary residency 457 visa as an interim step whilst qualifications are assessed, but best to get permanency ASAP after for there are some catches with a 457, reliance on having an employer being the primary one [ no sponsor or other visa and you need to find one quick like in 28 days or leave] and then secfondary schooling fees for kids could be a lot more expensive on a temporary visa.
Employer Sponsored Workers - Workers - Visas & Immigration