I once took a "jungle walk" tour in Costa Rica which was a simple excursion to the rain forest. But we saw wild McCaw parrots (5 feet tall!), monkeys traveling through the bush, poisonous frogs, live crocodiles (12 feet long and HUGE). It was a very cool tour.
In Aruba - there really isn't much. Gamble, golf or shop. Or go to the beach and tan. It is not a place of natural beauty.
Years ago, we ttok a tour in Aruba called "Natural Wonders". Tour guide drove us by the mayor's house, the librarian's house and a school teacher's house. We still laugh about thier definition of Natural Wonders!
We also enjoyed the river rafting in CR, fun and worth the money. However, just as we got in Puerto Vallarta adventure, we got some terrific 'bites' that were horrific and itchy for many days. The guides said there were no mosquitoes until after dark (and I don't react to most mosqito bites) and they seemed to come from the sand or the water. I would definitely rub some insect repellant on next time. I had to switch to formal gowns or pants for dinner as my legs looked hideous. So come prepared. In PV they told us not to use repellant for eco friendly reasons, but I wouldn't chance the 'itch' again
In Aruba, after covering the shopping, we enjoyed a relaxing time at Palm Beach.