10b/8b/3g
Museums not likely, activities prob
Ok, so I have no experience with the first 2, but last year we went with a 3g (and an infant) to Phily. Did Camden Aquarium and Legoland Discovery Center (my 3-year-old loved it, maybe too babyish for the older ones) the first day. We ate at Star of David Grill and stayed in Residence Inn Bala Cynwyd. We were going to go to Ben Franklin Institute on the way back, but between the mask restrictions and my daughter being happy with a regular playground, we just did that. I davened at Lower Merion Synagogue and the Kollel.
There are plenty of other activities in and on route to/from Philly.
There is also a citypass which someone might sell you at a greater discount on ddf.