Why CA? UW is not the small environment you are seeking but nothing with Engineering is going to be. UW is fantastic. If smaller/more personal is a priority please check out Whitman, Lewis & Clark, Univ. Puget Sound. Not sure how good the sciences are there but he is probably in merit range. Someone else mentioned Occidental. Good science, no engineering-- it’s pricey and he’s probably not in merit range.
I agree Colorado Mines is worth a look for Engineering and possibly merit. Small for en engineering school. Undergrad focused. Public schools and applications for merit are passing by quickly. So act fast.