You do not say what islands you are visiting before you get to the Panama Canal, if you could let us know we can give you some tips.
I would recommend that you do your own thing on some of the islands. Take a taxi just make sure you negotiate a price before you set off. If you go to a beach they will come back for you you just ask the time. It is far cheaper to do things this way. Just make sure that you have enough time to be back at the ship before it sails. We normally ask them to get us back about 2 hours before sailing time that way you will have enough time and can go shopping around the port.
Sorry Ihave now added Itinery
Sorry I forgot to put down Itinery we are visiting the following ports,Mayrea, Grenada Windward Islands,Margarita Island Venezezuela,Curucao,Colon Panama,Puntarenas,Puerta Quetzal,Acapulca Mexico overnight stay.