It is pretty early in the season. Be patient, unless the roster is too deep things will probably balance out. Coaches will adjust once they see various players perform. They are balancing player development and winning which is a tough thing to do, especially early in the season.
If the coach was there last year look at the players playing time. Did he seem to give a fair amount of time to all the players?
Most coaches will develop a playing time pattern that is somewhat predictable. I'd encourage your son to just keep working and improving his skills. Make the most of the batting practice and fielding repetitions. Ultimately, there is little he can do but battle for playing time. This is a mental challenge of trying not to do to much when opportunities are provided. Just stay relaxed and play to his strengths. Enjoy the experience and develop his skills.
I know this is nothing you probably haven't told him already. It is a journey that he should enjoy while working hard to improve. Best of luck.