I am guessing that you do have an offer, but if you aren’t 100% sure, I would make 100% sure that in exchange for your son applying ED, the coach is supporting his application. And I would ask what exactly that means, i.e. is he 50/50 to get in, or is he all but assured admittance.
My guess is that he is closer to 100%, but it’s always smart to clarify with the coach. My son’s coach was laughing at me by the end, because I asked him several times several ways if he really had an offer. He basically said as long as he keeps his grades in the same general place they have been and doesn’t stab anyone he should be fine.
He is at an Ivy, but it’s pretty similar to a NESCAC. I have a daughter (non-athlete) at Amherst. He is also solidly below the 25th percentile at his college. He is not getting great grades, but good enough, in a relatively difficult major. Also he is training and competing year round in his sport. It hasn’t been easy, but I don’t think he would change anything if he had it to do over either.
If you want to talk about that more, feel free to dm me.