First- congrats to your son! Some things to consider:
-I believe that ED only is binding for the first year. After that NCAA tranfer rules would apply. Binding would mean you would be required to put your deposit down and such.
-With ED, you also accept without knowing your complete financial package. This may or may not be a concern for your family.
-Has your son had a chance to talk with any players? Are they happy?
-What did your son's gut and your gut tell you about the coach? Usually that instinct is a good one if we listen to it.
- Is the school a good fit academically? Does it offer your son's major? Would he be happy here, God forbid, even without baseball?
I would say if the majority of those answers can be answered with a "yes" then I would say so long to the search and welcome to the school!!
Good luck and much congrats!!