It's never too late! If it's what you really want, you'll get there. Also, you can still do GCSEs and/or A-levels (distance learning, evening classes etc.), there are lots of options and ways to get there. This will give you a grounding for you to apply for your degree and might be easier to study for with two little children. Just explore all your options.
Have a read of everything. Loads of my friends have done the conversion course, mainly after science degrees. However, law is ultra competitive, there are so many people taking the courses (to the point that the number may be restricted, as there are just too many!).
Do whatever you can to help yourself, work experience (maybe part-time in solicitors office when kids go to school, even if it's secretarial it's applicable) etc. If you know anyone in law, pick their brains. Also, depending how you deicde to go about it, if you choose a non-law degree and then convert, the better your first degree mark the more likely you are to get awarded grants to help further study.
Don't underestimate how beneficial knowing what you want to do is, I wish I did!
Good luck!!