The shows are really good, and you can spend a whole day between shows & taking your time with the animal exhibits. If you are not really into the animal exhibits, then it's more of a half day to do the shows - but note that they're scheduled in such a way that you might take most of the day to see them all. Their exhibits are really nice, and you can spend a lot of time in with the penguins or wild arctic as nice respites from FL heat. Especially the penguins - it's literally freezing in there.
If you like to spend time at zoos/aquariums and you want to enjoy the shows, I think it is worth it. There are also some non-intense rides like the sea life carousel & the observation tower. I think it's a few bucks to ride the tower but you are rewarded with gorgeous views out over Orlando.
Your third party member could also take a detour onto the rides while the other 2 linger over an exhibit or two, or rewatch a show. Manta & Mako are fabulous roller coasters, hard to pass up for coaster lovers.