I'm mostly inline with 2Boys, but I can see a tiny bit of wiggle room.
First of all you have to apply for the All Academic game tryout, and to submit that with incorrect info would not be an honest choice or fair to other applicants.
To Adbono's point, a commitment to a D3 college _is_ a commitment, once the ED app is in. You're signing a contract that says you will attend that school if admitted (absent some limited mitigation circumstances.)
But that said, if ED app is not in, and taking into account that the coach doesn't have a "tip" with admissions, you could make the case that the kid is not fully committed until the app is in the mail. In that case, if the kid has another equally desirable target school (which doesn't seem likely) that does have coach tips and has not seen him play, but will be at the event, then maybe it's OK to go, but only if the kid is honest with the coach and says, "I'm applying ED by the deadline, but if a school of equal quality should offer me a guaranteed admission before that date, I'm going to have to weigh my options." Coach may not like that, but he knows the kid isn't guaranteed to be there next year, so that means he's looking at other options as well.
Of course the biggest PITA for your son in this situation is that he's going to have to do some RD applications.