I agree with its, that's not a question to ask directly, and I would bet the answer would be something along the lines of "your son will have the opportunity to compete for a starting position". That, when you think about it objectively, is a diplomatic non-answer.
Names or numbers of others being recruited at your son's position are also meaningless unless you know their order of priorities --- is it your son they want most or another player? Coaches have to court several players per needed position as there is no guarentee that an agreement will be made with their top choice, sometimes with the further consideration that a player signed may be successfully drafted. Coaches are also aware of the baseball grapevine, and they're not going to want specific-name gossip out there.
I'm assuming you've checked their roster for players at your son's position, their year, stats, and history of starting/playing. That's the known, established competition.