well that all depends...there is a ton of stuff to do there as a tourist. how old are the kids? interests?
the beaches are not 1&1/2 hours from disney. from disney you take i-4 directly to 528 and head east, maybe an hour, probably less and that will take you to canaveral & cocoa beach. Cocoa is ok - no cars on the beach, so if you have smaller kids, its better than New Smyrna which is a lil north of Cocoa. Canaveral is also there, which is pretty cool if you have boys or kids interested in space, pretty cool place to explore for a day.
Islands of adventure is a great park, the rides are awesome, but they don't have the shows like Disney. If the kids are younger, say 8 or less, it might not be the best place as the rides are usually designed for more of an older crowd there. On the pro for IoA though, you can drink in the park - can definitely make a day with kids alot easier to take
There are tons of things on International drive, from great go-cart places to mini-golf to Ripley's to shopping, to great restaurants and more. Definitely drive the length of I-drive one evening, its an experience if nothing more.