One really quick stop we like to suggest to groups when visiting Philly is Love Park, otherwise known as the John F Kennedy Plaza.
This park is quite small but serves as the 'grand entrance to the Benjamin Franklin Parkway', getting its nickname from the iconic reproduction of Robert Indiana's Love Sculpture. This sculpture fits perfectly within the 'City of Brotherly Love', and has been here since 1976, minus a couple years in between where it briefly moved homes but soon found it's way back.
The park itself sits right in between the Philadelphia Art Museum and City Hall, giving it a prime location to many of your next attractions, plus really great views of the city overall. This stop is great for a photo opp, a quick history lesson on both Robert Indiana and Edmond Bacon, the famed city planner who designed the park (yeah, Kevin Bacon's dad), and good reason to stretch your legs and get some energy out. There are several ping pong tables and bistro style tables throughout to relax and enjoy the scenery, and there are even food trucks lining the way most of the time.