Poptime, dbg_fan has it right re the impact of Early Decision on the situation.
Early decision is an admissions practice, nothing to do with baseball or the NLI process or the NCAA.
Early decision is meant to help kids whom the school would definitely admit in April, and who have decided which shool they are sure is their # 1, both to get their decisions made before Christmas. This gives both sides security and also saves the student a bundle of time and money since applying to second-choice schools becomes unnecessary.
Even if you don't get in ED, you can continue to apply through the regular process and hope to make the cut in April.
In real life, kids break their word on ED all the time. They apply ED to more than one school and accept at more than one and then sort things out later. Some will even continue applying all spring, thinking they have a "safety net" school in the bag but can still "look to upgrade". The spread of this practice is leading many schools to abandon ED procedures altogether.
What all this means is, ED is a "gentleman's agreement" situation, where persons of honor consider themselves bound and others flaunt the whole notion of being honor bound. But in any event, it governs only initial admissions to a school and has no bearing whatsoever on the student's commitment to stay all four years, nor on whether the school will keep him all four years.
The advantage of getting in ED is that if you are one who lives by your word, and if this really is the situation you would rank this school # 1 on your list anyway, you can have all this squared away even before fall grades come out! That means your son won't have to sweat the tests so much that spring, and can go out and play baseball this spring purely for the fun of the game and without feeling like he has to impress somebody somewhere.