Wow! Has Fishtown changed! I've lived in the Philly area all of my 46 years, and it used to be a working class, Irish-Catholic, sort of rough neighborhood. When I was little, I had cousins who lived there, and it was just a basic, rowhouse sort of neighborhood where dads went to work at the old Schmidt's brewery, or maybe a little further up north at the Stetson factory or Tastykake. There was a lot of industry up in north philly back then. But that all died out and by the time I was in college in the early 1980s, Fishtown was a real mess, lots of drug dealing, etc. But today, you'd never know it! It's really the hot spot in the city right now, with a very tight community, lots of artist-types, and plenty to do. It's neat, and cute, almost like a little village. I think you'll love it, especially if you're near the river. The real draw seems to be the riverfront area.
Another post mentioned Mt. Airy, but that's not really close at all. Mt. Airy is completely across town in the sort of "arm" that sticks out of Philadelphia to the west. Fishtown is right on the Delaware River between north philly and center city. I'm so glad that it's an area coming back to life.
I don't have small children, and I only go down to fishtown occasionally, but I would suggest you start at the library. There is a beautiful old library at 1217 Montgomery Ave. I think it's in an old firehouse. I'm sure they have listings of community events, neighborhood groups, and story times for even the littlest ones. It's always good to get to know your neighborhood library.
Welcome to Philadelphia! I love the city. There is so much to do here. It's a big city, but it has a very small town/neighborhood feel about it. My youngest son is starting college at Temple University this fall (where my husband and I went to school many, many years ago), and he's excited about having Philadelphia as his college campus. There's so much to do and keep you interested!