my friend has a giant pool too and what she did for her birthday was she got a huuuuuge tarp (you know, the blue plastic things people use for backyard skating rinks?) and dumped sand on it all around it she put up beach umbrellas and had a bonfire when it got dark. she had a "clam bake" too.... but they didnt use clams, they used marshmallows
anyway, it just a suggestion...