How many is too many pitches? Need Advice for son.

My 10 yr old son is playing tournament ball now. He pitched 6 good innings on Saturday (most he's done before was 3). He pitched about 90 pitches. Sun he pitch 3 innings and another 40 pitches. He seems to get stronger and more effective the more he pitches and deeper into the game. I read Dick Mills site and based on that he's throwing too many pitches. My son says his arm feels just fine and after his second outing Sunday he said the arm was "just a little" sore. Is he OK to let soreness be his guide. Should we "limit" his pitching time regardless of how he feels. Also is there such a thing as "where" his soreness should be if he's pitching correctly. His soreness is just below the top of his shoulder on the arm. I guess this is better than the elbow. He's in tournament ball now and they are play mulitple games every day. 1 Fri, 3 Sat, 3 sun, 2 mon so the team needs all pitchers to pitch in. Please advice on how I how limit my sons throws. Should I ice him down after games? If so for how long and when. Can you direct me to some archieved info on this subject or good artiles to read. All advice appreciated. Joe.