OK... here's another thought then...
Try using a 400 speed film and rating it at 100. You are shooting in very contrasty light so using 100 film is going to exaggerate that, so you might as well use film that has a wider latitude. You will need to underdevelop(e) the film by 3 stops, regardless of the developer you are using. No filters, no tripod (not really practical at a pool setting with kids anyhow is it?)... the fill flash suggestion could be a good bonus for a rather surreal look, but leave the flash set at 400 ISO, not 100, lest you melt your subjects.
Just food for thought...

Ray