My son will apply to 3 in-state college engineering programs? To what other affordable schools should he apply?

Colorado has a reciprocity agreement with New Mexico. Students who live in Colorado, but study at a public university in New Mexico, will pay tuition that is similar to that of Colorado resident attending a Colorado University. (this will also be the same for a New Mexico resident studying in Colorado). Perhaps there is something available there.

Don't know how prevalent "full rides" are for engineering, although I do know someone who got a Gates Scholarship for a full ride for undergrad and grad school in engineering. Those other schools you mentioned are private schools, so tuition will be much higher than your in-state schools.

In general, the more of a "catch" your son is for a particular school, the more financial aid he is likely to get. Schools that aren't necessarily the "Top 10" caliber want to attract highly-able students and will offer them more aid to entice them.

BTW - Don't count on getting a year of college credits from AP exams. [That would mean 30 credits!] Schools don't necessarily give credit for AP exams [and if they do, it would be only for scores of 5, most likely], although they sometimes DO waive certain pre-requisites for an AP score of 4. It depends totally on the school.

You don't mention his having taken the PSAT, which is the source of scholarship money [though not a lot] for students who score in the top 1%. Don't know if there's anything similar for ACTs. And, money he gets from the federal government will likely be in the form of loans, which will also have to be repaid, unless he qualifies for Pell grants or something similar.

A really good engineering school is Harvey Mudd College in California, but it's definitely not cheap!

You could wait 20 years college doesn't have an expiration date

He should see what individual scholarship programs those schools have.