Hi bluefootedpenguin
Very interesting views about embarking on a medical career- I am only just starting out as a doctor but I was a graduate student and am 34.
From what I've seen so far I truly agree with the other doctors posting on here...I know already that hospital medicine is not for me, GP represents the best possibility to have some 'work-life balance' whatever that is 
ok let's say you do become a medical student- don't worry too much about being sent miles from home, at medical school all the parents were given 'special circumstances' and were allocated to placements at nearby hospitals, for the duration of clinical training.
Also, the med school seemed v helpful in terms of taking time out etc. To put it bluntly, as a student you can just walk out of the hospital if there is a crisis at home, if you or the children are unwell you can just stay at home, you do have lots of free time in reality.
However, as a doctor this is just not possible...you will be on the rota, have to do late finishes, work wk ends, plus things always seem to go tits up at 5pm when you are planning your escape out the door!
I would add- don't panic about founDation placement jobs (FY1 &FY2)- if you have children you will be automatically allocated to your first choice foundation school, which is a huge bonus, then it will vary but most will take into account where you can realistically travel to.
A good friend of mine at med school got allocated Scotland when she was settled in London with her husband and TTC...her transfer request got turned down so they are living apart for 2 years, she is nearly 37 and they are about to start IVF, she is utterly devestated that her career has started out like this, resentment has set in esp considering that she may not be able to jhave children.
In a sense, you are in a good position that you have your children already rather than having to take time out for mat leave etc. However, the above posts clearly spell out that it's not all plain sailing once you have qualified.
Good luck in your decision making. For me personally, I love my job and am so glad I went for it...however, I'm starting to panic about when I will have kids, I am fully prepared to be a pregnant junior do ctor but god knows how we will manage childcare, finances etc. :(
Sorry for the very long post! hope some of this helps :)