I did. I started last September, when my DC were 4 and 18mo. It is hard, but for us it's easier than me working full time, as I get the same holidays as my DC, and the whole summer off. So really, I actually still feel like a SAHM apart from frenetic uni activity for 3 months in winter and 3 months in Spring! :)
It is hard to study after cooking dinner and getting everyone to bed but I manage it, and childcare costs were not too hideous as DC is at nursery in the mornings and DC2 at a CM. I spend as much time with them daytime and do as much work as I can in the evenings and weekends, when DH is about to do most of the childcaring.
I am hoping 2nd year will be easier, as DS1 starts school in August and DS2 nursery. It's tricky planning childcare, as it can't be done far in advance as my timetable changes every term. My head of school is accommodating though, and gets the timetable to me ASAP, so we plan from there.
I am glad I did it sooner rather than later; I almost waited to start this year and I am so glad I just went for it. Terms go so fast!
Studying with young DC is not for everyone but it is working out great for us, as I am getting on with my plans for a career after both DC are at school, and they still have me loads of the time.
Good luck whatever you decide :)