What else do you like? Beer? Monks is probably one of the best beer bars in the country (been a James Beard finalist like 5 times or something). Museums? The Barnes is certainly worth it if you’re interested in Impressionism. The Philly Art Museum is pay what you want (free) Friday evenings and the first Sunday of every month.
I’ll be in shorts and t-shirts next week, but some Floridians I know are in sweaters when it hits 60, so it’s on you to decide that.
Genos and Pat’s are tourist traps. If you’re into that and can accept that you’re not getting a great steak, then by all means go ahead, but I would steer clear personally. South Street is fun, the Reading Terminal in center city is awesome. Dinic’s Roast pork sandwich in the Terminal is what I’d recommend, they’re so good. It’ll be warm through the end of September most likely, just bring a hoodie for evenings. If you like weird stuff the Mutter Museum is a must see. On South Street the Magic Gardens are neat. If you like nature you could trek through Fairmount Park or Wissahickon Valley Park.
Oh and for a great place to drink with fantastic views, go to the Cira Green in University City. Very popular with the college kids in the area.
As cheesesteaks go I suggest Lee's Deli in west Philly, simply the best cheesesteaks I've ever had. Failing that Carmen's in reading terminal market in center city is awesome too. If you want a classic, archetypical cheesesteak though, go to any corner pizza shop. I always suggest getting provolone cheese, peppers, onions, and mushrooms.
You should also check out the Bok Bar, a roof top beer garden thing in south Philly walking distance from Pat's and Geno's with an outstanding view of the city.
Also in south Philly is "John's Water Ice" if you want good quality, authentic Philly Italian ice.
While you are at the art museum remember that there are a few other top tier art museums in the area too, like the frankstitute.
If you like nice looking buildings 30th street train station is a really beauty and so is the central library on vine street. The art museum and 30th street station are actually connected by the river path which is a lovely walk.
Speaking of walking take some time to just walk around Rittenhouse (south west end of center city) and/or old city (eastern side of center city) and look at the pretty houses and cute neighborhoods. Some of the finest urbanism in America.
I hope you have a good time on your trip and don't be shy about asking me more questions.