Certain specialities lend themselves to part-time work to a greater extent than others. For example, as a pediatrician or internist, one can always do ER shifts on a part-time basis.
Psychiatry is a wonderful speciality for women with kids.
I have 4 year old twins and am a child psychiatrist. I love psychiatry, but I also loved surgery in med school. The decision between the two was a lifestyle decision, and one I'm glad I made. Otherwise you will resent your patients and this destroys good medical care and any chance for personal satisfaction. Think carefully about what you will need in your life to be happy and make career choices in medicine that will address those needs.