The Wave Waterpark in Vista (San Diego) is great! Just big enough for the older kids but small enough and enough activities for the younger kiddos (and not too far from us in the IE). The Wave Waterpark is offering a great deal for fun! We go there every Summer and spend the whole day, this is a FANTASTIC deal! They have free parking too!
Grab cheap all day tickets to The Wave Waterpark on May 21st, just $5 admission for everyone from 1-4pm (no advanced tickets required)