Regarding Legoland (in Carlsbad, North of San Diego) they do have a water park but you have to pay admission to Legoland and then an additional fee for the water park which together will be EXPENSIVE, so I would not recommend it. Also, Legoland and the Waterpark there can't seem to decide what age they are geared for. They have few rides that are intended for those over 10 (only 2 rollercoasters and 2 large waterslides) so you may want to consider taking the kids the beach and rent boogie boards instead!! Good Luck!