Something that we did that was pretty cool was an overnight at a houseboat. But if the kids are coming with you, they might get bored (hell, even I got bored after a few hours, lol). It's a different experience, though.

At Coconut Lagoon we stayed at a Bangalow, facing the backwaters. Funny enough the pictures in these two websites don't do much justice to the place. At Coconut Lagoon we arranged for full board with breakfast, lunch and dinner. And they had Ayuverdic treatments as well, though we didn't try them.

http://www.karmakerala.com/kumarakom/coconut-lagoon.htm
http://www.nivalink.com/coconutlagoon/index.html