There are specialties where those practicing in the specialty are very family friendly, such as family practice and pediatrics. There are specialties that have little or no call, such as dermatology and pathology. What I have found to be more important is the situation, and the people who will be surrounding you. If you need to make a late night run to the hospital to deliver a baby, it's nice to have a flexible staff who pay a little attention to your young child. On the other hand, you can be in a very family-hostile environment while practicing as a dermatologist.
So follow the specialty that is the best fit for you. You can always choose the situation where you will practice.
I'm an Ob/ Gyn... YOU might say how un-family friendly! but I Find it to be ok...I have great partners, and they are all very supportive and we cover for each other. I love what I do and that benifits my patients and my family both.