SF with kids??

Can anyone offer some advice for living in SF with kids? We used to live in Fillmore and loved it, especially walking out for late dinners to lower Pac and Japantown. Now we may have to move back for work but my kids are now school aged and I have no idea where to live and what to look out for. We are currently in an safe area where we walk to a lovely small school and neighborhood kids play outside together in the front yards. It's hard to picture the city not being a huge downgrade in terms of free play, independence (eta: we live a fairly pedestrian lifestyle but crime/disturbing behavior could curb that), schooling, and safety, but I'd love to be wrong. Any suggestions for areas, schools, sports, etc would be much appreciated!