Network, network, network. Smart to ask questions here... even better to have son ask questions of his baseball playing friends about the clubs in the area. If any of the tourneys he desires to play in next year are fairly local, go to those and have him introduce himself to coaches. Over the last few tourneys this year, ask around (with as much reasonable discretion as possible). Heck, you have a good reason for looking at other options. You may even want to ask the current coach who goes to those desired events. If he is sincere in his efforts to help the players, he very well may oblige with helping your son find the best fit.
A few side notes... be aware that true OF's generally don't get much, if any, scholly $ unless they hit A TON. So, academic $ will likely need to be the focus. Regarding the arm issue, don't offer up anything until he has an actual tryout. Then, be careful to include that he is fully cleared and healthy, will just take some time to get arm strength ramped back up.
That said, don't rush back from that type of injury. And make sure he keeps his mechanics correct. Many players I see recovering from slap will modify their arm angle to get back on the field sooner and it hurts them in the long run.