Being 1.5. hours away from Panama City makes a big difference. I assume you're going to be staying at some resort. Beaches are OK at the resorts but not spectacular, like Mayan Riviera beaches. Water is murky, not too clear even on a sunny day. Food was very simple (at Decameron). Panama City used to dump all or most of their raw sewage into the ocean until not too long ago and it shows. Plus, there is a lot of construction along the shoreline everywhere.
If you are staying at or near the Decameron resort, take a trip to the Fishermen's Village between Decameron and Costa Blanca. It's very authentic and not too touristy:
I was going to suggest that you should stay at the Hard Rock Hotel at Panama City at least for a few days. The place is simply amazing – brand new and super cool. I believe this is the biggest HR Hotel in the world. Crazy club parties at the bar level every night. Lots of good action.
Gamboa boat ride was good. We saw some wildlife, but not too much. Depends on a day, I guess. Bear in mind, it rains almost every day in Panama. We did rent a vehicle and drove around. On the way to Gamboa, we took a wrong turn and got lost in the rainforest during a tropical rain. Ran into a group of Canadian potheads from Toronto who turned out to be really nice guys. They showed us the way out of the forest and on the way out we have also found a wildlife observation deck/station, where we saw a million hummingbirds. I've never ever seen anything like it.
This is Gamboa:
Canal is a must see. Seeing gigantic ocean liners passing by through a 30'-wide trench is nothing short of spectacular.
Casco Viejo is an old district of the downtown that is being "revitalized". Nice, but nothing special. Lots of armed military men on every corner. Panama City has a hugely over-built downtown. There were no height or style restrictions there until now and it shows. Everything is eclectic architecturally.
Slums are everywhere other than downtown and they are quite striking in contrast:
We had a local host, so we ate at the restaurants they've recommended. Food was good in every place we ate. Not cheap, though. Golf was nice also.
PM me if you need any more details. Sorry for the long post.