Herrington South (western shore across and a little north from Tilghman Island) has a large pool that the kids would love. There are some very nice marinas at Solomons Island. The pool at Spring Cove Marina has music piped in the pool. Dive in and take a listen
Their grounds are also very nice for a picnic. Since you're going to keep it to apx 30 miles a day make sure you get an early start and get off the water by early afternoon if possible. At that time of year late afternoon T Storms are not uncommon. Have a good trip.