We also are thinking about the Mardi Gras or the Luau. Although I think the Mardi Gras would be fun, I'm leaning toward the Luau. It's our first night, we have 3 kids as well, a little younger than yours. The Luau is right at the hotel, it has fire eating men, and hula girls, I think that would be fun.
Have fun!
Leah