I am going to try and read between the lines a bit here. It sounds as though there may be some angst about whether or not your son will get a valid/fair look from the new coach. It appears he has already made inroads as far as knowing some of the players which is a good thing.
In my mind, the best thing he can do is let the 800 lb gorilla off of his shoulders by not worrying about whether or not he cracks the starting line-up right away. If he is already a college prospect then his status with the new hs team will not change that imho. He needs to focus on those things he can control (hustle, being productive in practice, etc.) and let go of those things he cannot (who the coach intitially decides to start). The cool thing about baseball is there will always be opportunities to perform due to slumps, injuries, attitudes, grades, and what not.
Work hard and remain focused on the task at hand. Most importantly, keep the mouth closed at all times. Actions truly speak louder than words. One thing he can control is to be the first player to arrive and the last to leave. He can also become known right away as the hardest worker on the team and willing to do all the team's dirty work if necessary without complaint. After that, let the chips fall where they may