This is getting a little dated but is a reasonable starting point. It lists every college, the % of freshmen receiving merit aid, and the average dollar amount. You can find the latest information for any individual college in their Common Data Set.
http://www.nytimes.com/interactive/2012/07/08/education/edlife/8edlife_chart.html?_r=0
I think it’s quite reasonable for you to do a preliminary cost/merit aid filter and let your son choose from the results. I did a similar filter but for need based aid for my D.
I was surprised that D got merit scholarships at all 4 colleges where she was accepted, ranging from $16k to $27k per year, and in state tuition at an oos university (her safety since she did not want to attend instate).