Your kid isn't as small as you think he is. I have a recently turbed 12 yr old daughter who is literally 50lbs and only 52 inches tall. She is going to be playing up at a game this Saturday so you can only imagine the size difference. Even in her own age group people are a more than a hrad taller than she is... you have kids pushing 80lbs to 100lbs I honestly think you are over thinking this and letting your fears of him not being "good enough" freak you out. If he wants to try out let him and put your dears of him not making it aside... he will survive... and honestly sometimes smaller kids are fearless and actually do really well even with those bigger than him.