Stephanie,
Please don't knock yourself out. Don't give in to the pressure of your son having to be the best player on the team or that he is not good enough. He is 4 years old. Enjoy this time. IF anything, get him a Tee Ball set and just practice how to hold the bat, his stance, batting, and catching the ball. You can purchase a set at Wal-Mart or Target. Academy has good prices too. He will get better, but it will happen as he plays more games. Mind you, his practice attention might be about 15-20 minutes, so be patient. By the way, there are boys who are 8 years old and still playing in the dirt. Good Luck!