What is proper etiquette?

Before the game? I would counsel against it. After the game, maybe. Do the coaches know he will be there, and did they ask him to say hi?

I'm pretty sure that NCAA recruiting rules limit the kinds of contact that coaches are allowed to have while on the road for games. When my son was in a similar situation, a coach said "I can say hi, but that is about it."

In any case, I wouldn't try to pull them aside pre-game. They are busy.

I think it depends upon how well you know the home coach. My son and I went to a local D1 game (he was being recruited by the home team) against a school he had gotten a letter from. Son talked to the home D1 coach, pregame, and the home D1 coach actually introduced him to the visisting coach when he found out my son had some interest from the visiting team. We were just going to talk to the local D1 coach and observe the other team.

However I think there are some coaches that might go in a different direction

How about holding up a poster over the center field wall that says "Patriot Son Hits it Here"?

We have visited with both coaches earlier in the year. We will notify them that we are coming to the game. I think a "Hi, how are you doing" will be about the extent of the conversation. The host school is about 100 miles away and the visiting school about 400. It's about seeing a great game and continuing to express interest.

SOS, I like the way you think. By the way, I could use a guy that thinks of creative ways to get the message out. Love it! Too bad they like him because he is a LHP.