Well johnj, it sounds as if you are on the right track. You just want what's best for your son and we hope after reading the advice here, you'll be able to guide him well. Sometimes posters that have studs for sons don't understand how much harder it is for players that aren't studs. But you have your priorities right. Sounds like you will be enjoying this year!
If he is as good as you say, it won't take long for him to stand out to the coaches even if he is on the freshman team. They will talk and he will be moved up. That should be his goal. Tell him that and see what he does. If he makes it his goal then he is ready. If he starts "playing down" perhaps he's not ready for varsity afterall. But given what you've told us, he'll want it and go for it. Enjoy it...we are in our last season and man did it fly by!