@Bapi, I hope you are reading these posts! Your son will mess up his future if he tries to enroll in two universities. They will find out (it doesn’t matter that they aren’t both UC schools) and he will have no place to go. If the moral considerations don’t bother you, the practical ones should.
Almost everyone who applies to college has the dilemma of trying to choose. You just have to pick one and go for it. Once you’ve chosen a school, you really won’t think about the one you turned down.