When do you say no?

My S told coaches as soon as he knew either (1) he had absolutely no interest in the school no matter what or (2) he had two other offers (independent of each other) and either was fine.

Goosegg, this is the summer of OP son's rising senior year. 

Sr moment.

If these offers are open ended, you say no after you committ.

Again, congrats on the offers.  It is great to have choices.  I would only say "no" only after you've told a program "yes".   I appreciate your feelings of not being rude, and I totally understand.  However this is one of those times where your son needs to put his interests first.  I recall going through this with my son too.   He didn't want the coaches not to like him, and he always put the team first.  Well, this is one of those situations where you have to take care of your own business first.  These coaches do this everyday, and they probably know more about your situation than you think.   Your son can give them a call when he is ready to give them the news.  I think any respectable coach is going to wish him the best going forward.  My son kept in touch with a couple coaches (after he committed) who asked him to keep in touch just in case something happened with the Admissions process.  I think it spoke very highly about him and them.  As always, JMO.

Good luck on your upcoming visits and decision.