Closer to museums and activities is Schenley Park - another large, beautiful park with nice trails and fewer dogs. From there you can see Phipps Conservatory, Carnegie Mellon and drive into Oakland. When you do, you may want to check out the outdoor carousel at Schenley Plaza. The park has little food stands and seating, and is a nice place to take a break after visiting the Carnegie art or natural history museums or the library.
Looking at Schenley Plaza now, it's hard to remember that a few years ago, it was an ugly parking lot that we would trudge across to get to the good trucks (an oddly legal form of food service in Pittsburgh) serving graduate-student-priced food. The trucks are gone now - along with the low priced food - but Pittsburgh has an extra park instead of a parking lot. Just the kind of happy thing that can happen in a shrinking city.
Finally - we almost held the festivities at Hartwood Acres - which would have been beautiful, too.