portofino is nice
personally (i said personally, folks) i'd skip zip-lining and see the lamanai ruins instead. its a long, whole-day tour but you really get to see belize - the mangroves, boat up a jungle river, see mayan ruins, be in the rainforest, we even saw monkeys there...its really cool. see if jan can hook you up with tanisha tours to do it. daniel is the best!
a must-do is a snorkel at hol chan reserve and shark ray alley. they are usually combined. you wont regret it and will tell stories of it for years to come.