drrich2
Contributor
I would take the trip to Lamanai on your last day. It is a REALLY fun excursion.
I believe this is what we did on a 1 day stop on a cruise; it entailed a boat trip up the New River, where we variously saw bats on a sheltered part of a tree, a monkey (in an area they put out food), some crocodiles, and lush vegetation, then got off the boat and went on a rainforest tour, visiting 3 Mayan ruins (basically pyramids) - Jaguar Temple, Tall Temple and Mask Temple, if memory serves, and the latter 2 we had the option to climb atop (and get some sweet photos).
This was a good tour and I also recommend it.
Richard.
P.S.: Granted, I picked it because my wife gets annoyed if I book a scuba excursion at every stop.