I've been wondering what a float system with a fountain sort of thing in the center might do. They have these little plastic baby pools for kids that might do for a float system, not the blow up kind, the hard sided kind. It might be possible to either make a little central waterfall or a fountain that doesn't go too high, you don't want wind to blow the stream so it doesn't land in the pool.
The idea would be to make floats in circular sections so that a hole in the center existed which could house a kind of cone shaped fountain or waterfall. This could be fun and not all that difficult. The trick I've always found is making the floats. Most of my Styrofoam floats have left a lot to be desired. I probably should look for a better float material or at least a better way of cutting the Styrofoam.