Definitely do SITE or a similar program at another university. It will do 1 of 2 things: either cement his decision to do engineering as a career, or turn him off to it and you have then saved yourself a ton of money and time to know that! 
HIGHLY recommend doing a week-long engineering camp, and if you do this at a university you are seriousy considering attending (i.e., your shortlist), it will further help in your decision to attend there or not. My son did 2 different camps the summer between junior and senior year at 2 universities he was considering. He was able to rule out 1, based on that experience alone. Families who have done SITE or similar have great things to say about the experience. We found the money well worth spending, because son got to ‘try on’ the university and it helped greatly with his decisions.