my advice is that you find something that you truly love to do, because if you don't love what you do, the time you spend away from your kids and at work will be utterly miserable.
only you can decide if you would be happy with nursing or becoming a physician. if you decide med school, as you can see, there are many, many moms who make it work each in their own way. if you have to work anyways (and don't have the option of SAHM or don't want to be SAHM), what would you rather be? the training may be long, but if your practicing medicine for a good 30 yrs, its really all relative.
if you chose med school, sounds like your kiddo would be close to school age by the time you started, making it much easier to be away all day....
one last note...you don't have to have it ALL figured out right now...i'm in my 3rd year of med school, just had a baby, and am still trying how to figure out how this is all going to work

as stressful as it is, i don't think i would have it any other way.