I'd guess that pathology, radiology, emergency medicine, and ophtho would be some of the most family-friendly specialties, especially after residency. I'm guessing this based on little or no in-house call and more regular hours.
Most primary care residencies are not that bad, though this is probably depending on the institution. FP, Peds, and medicine are all only 3 years. Some programs use a float system for call (this means little to no overnight call ~ 10 months of the year with ~2 months taking only ~6PM to 6AM shifts.) Outpatient rotations often give some weekends completely off. At my home medical school, almost all of the females in internal medicine are married and over half have kids.
I love surgery but I am also single and don't want kids. I could see that it would be very difficult working >15 hours a day and taking call every third night if you had a child. On the other hand, if you are surgically-inclined, it may be worth checking out ophthomology or ENT, which may have more predictable hours and less call.
As for the boards, the higher, the better, but if you were to get a 220 and were dying to do radiology, I'd stilll go for it. You may not get as many interviews as someone with a 260 who is AOA but I've known lots of people with average scores and grades who matched into very competitve specialties. I think as long as you beat the national average, you will have your doors open. And if Step 1 doesn't go as well as you want, take step 2 early and do very well. Programs will be impressed with your improvement.
Have as much fun as possible during time off during the summer. If there is something you are particularly interested in, shadow once in a while, but not so often that it becomes stressful or not enjoyable. Do all of the fun things you like- you have plenty of time 3rd year in rotations to get a taste of different specialties.
good luck!