Here’s where you can find out what the D3 programs are, where they are and how good they are. From there you can make a list and research them academically. Look up average admission gpa, SAT/ACT scores. Don’t be scared by list price. He may qualify for need money.
There are D3 programs where the only requirement is the money and a pulse. There are also D3 programs that are part of the state university system. NAIA and JuCos are another option. There are D3 JuCos.
Does your son know what direction he wants to take in life? Is it worth paying for even a public university D3 if it doesn’t lead anywhere in life? However, there are technically oriented colleges.
If your son isn’t going to get anything out of college academically why not look for a quality adult summer league?