You didn’t say how your son reacted to the flowchart, but it reminds me of this (very simple) online quiz that I had my DS take when we were starting to think about types of colleges: https://www.forbes.com/sites/maxinejoselow/2015/07/29/college-matchmaker-quiz-find-your-perfect-fit/#1a9a6a583e3d
Also the Colleges That Change Lives book is broken down geographically, I believe, and is (I think I recall) made up of mostly smaller schools, some of which I know give great merit aid.