I'll just offer a few thoughts, having done four full transits of the Canal, all through the original locks -- the same ones the Summit will use (barring a very unusual operational issue in the Canal). I am fascinated by the Canal (obviously), and I think it would be very interesting to visit the Agua Clara Visitors Center. (Take a look at the reviews and photos on Trip Advisor.) You get to see those new locks up close and, if you are lucky in the timing, you'll see a neo-Panamax ship going through.
It does seem that the tour you are talking about, however, combines the Agua Clara Locks with a visit to Casco Viejo (Old Panama). We were there last year (having docked at Fuerte Amador, just outside Panama City). We walked around; it's a colorful and interesting bit of the City, and while I don't think your tour would spend seven hours on a bus, I personally would not take a bus ride across the Isthmus to visit Casco Viejo. Just speaking personally. (Others who have driven across from the Atlantic to the Pacific and back hopefully will weigh in on the experience.)
Also, please keep in mind that your next day, the day of the full transit, will be a very long, very hot, very humid one. You'll want to be all over the ship, seeing the locks from all different perspectives. Only you can judge whether you want to precede the day of the transit with a full-day tour.
I hope that's helpful.
Enjoy whatever you decide to do!