My vote is for an all-inclusive resort. All the benefits of a cruise (food and activities included) plus alcohol and no motion sickness!
We've done all-inclusives in Dominican Republic (2 times - 2 different resorts), Mexico, and Jamaica. All were on the beach and included kids club activities (and organized teen activities now that I've got a teen). The kids activities are great - they make tons of friends from all over the world (my kids have pen pals in England and South Africa they still write to) and do all kinds of cool stuff both day and night; meanwhile, I lounge on a beach chair with a cool "Mommy drink" and catch up on my summer reading, waving as they go from one activity to another. We go off-property for a day every trip and have gone horseback riding on the beach (DR #1), to visit Mayan ruins and go to a snorkle park (Mexico), scuba diving and then to swim in a lagoon with glow-in-the-dark algae a la Scooby Doo (Jamaica), and swimming with sharks and sting rays (DR #2).
My friend (also a single parent) and I take all five of our girls every year - our summer trip to DR for seven people for 7 days all-inclusive (including airfare and the shark swim) cost $200 LESS than 7 days for 5 people at Disney with free dining...so the prices are attractive.
You have to do your research and plan carefully (but if you do Disney you're used to that!) - but you can really do some great things. Next year we're looking at Costa Rica and doing a zip-line through the jungle