Chapman and Santa Clara may be a reach depending on the SAT scores and are definitely going to have an upper level income feel to them that may or may not be comfortable. Seattle U is a solid option, UW Bothell for a smaller campus feel without the competitiveness of UW Seattle but all the same resources. UW Seattle will be a reach with the SAT for the major and will be a bit brutal (as well as very competitive) if low on college prep.
I would look at Colorado State, you’d get WUE exchange pricing (auto merit) with the WA residency and a solid but less competitive group. Western WA is a solid option and would be a great safety. If willing to pay full price UC Boulder is an option but as with Santa Clara/Chapman will have a high degree of affluence.
How high is the rigor with the 4.0? That will play a factor as well in terms of options, it is a solid GPA but if low on rigor (and the low college prep makes me think it may be) you will want to factor that in as CS is one of the most competitive majors right now.
If he wants to be a big fish in a small pond, you’ll want smaller schools and lower ranked schools in general, and for the major which can be hard to find unless you are looking at LAC’s or Honors Colleges. To that end, perhaps look at Barrett Honors at ASU, the honors college at Northern Arizona.