I'd be happy to share my experiences so far, as it sounds like we have some similarities! I graduated from year 12 in 2003 (didn't do the QCS test though so didn't get an OP score), but didn't want to go to uni at the time so got on with life in general - a few TAFE courses, working retail/hospitality, got married and had the girls... then last year, I decided it was time to get myself educated! I enrolled in the STEPS course through CQUni, which is a tertiary prep course and sounds like it'd be right up your alley given your current situation - it has four subjects (computing, maths, language & learning and tertiary prep), which start you off with the basics you'll need so that you're prepared for further study. So far this year, we've been taught step-by-step how to research and write an essay, done lots of work on concepts like behavioural profiles and learning styles (which has been very handy as it gives us a better insight into how we can get the best results by tailoring our study methods to fit our personalities), and lots of other stuff that I feel will really give me the tools I need to pursue further study - AND it's been a good kind of 'practice run' by learning how to juggle home life before I dive right into the 'big' courses!
My uni offers this course (local universities near you should offer similar tertiary prep programs for 'mature-aged' students) in several ways - external, day classes (part-time), night classes (part-time, I decided to take these ones as I can't afford the daycare spots and needed to be in the classroom to stay motivated), and accelerated (full-time during the day, but those students graduate in half the time).
It's free for students who qualify (all you have to do is be an Australian resident, meet the criteria and sign a form promising the government that you'll do your best to finish the course and not waste their money!), all I have had to pay for is some exercise books and pens, pencils, calculator etc - less than $100

My DH is at home with the girls at night and he's pretty slack with their routine - I have dinner prepared before I go to class at 5:30 and when I get home at 8:30 I have to bath them and put them to bed, but it's no big deal for us - it's only 3 nights a week and they're at an age where I don't consider a strict routine to be hugely important... if DH wants to slack off and just watch TV and play with them, I'm okay with it

So I'd suggest having a look into a similar course where you are, I'm really enjoying dipping my toes in and learning what I'm going to be in for when I start whatever courses I decide to go with next year Good luck, I hope you can find an option that works for you! x