Citizenship 2018

Hi everyone
Haven’t been on this forum for a while now
I have started my journey here to get a 309 visa then on my 100 visa. This forum has been there for me throughout that journey
Since then my 2 children have also joined me here and we are all PR and enjoying our lives here.
The next stage for us is to apply for citizenship.
We have met the criteria and I am now looking at the application process and checklists and what documents are needed.
I’m telling you it brings back memories when I was doing the 309/100 visa
So my situation is this me and my daughter 12yrs old will be applying online while my 16yrs old son will have to apply on separate application online on his own.
First of all is this correct?
If someone in here has gone through citizenship journey can we share some thoughts please.
Would like to know how long process is generally and what’s it like in general...
Looking forward to hearing from you
Cheers!