Pitching practice questions for a 10u player

Quality practices 3x a week should be fine. If possible, pitch every other day, not consecutive days to give the body a day to recover, if possible. In tournaments, remember most 10U games never go 7 innings unless its the championship game. Most are timed and starting pitchers will only go 4 maybe 5 innings a game. Many times you can use 2 pitchers so no one pitcher has to throw 200 pitches in a weekend. My 12U DD once pitched 3 games in a row including a 9 inning ITB, I estimated she threw 400 pitches that day including warm-up and between innings throws. She was sore for 2 days and the only time we felt the need to ice her shoulder/elbow.

Lastly, I'm a big fan of practicing pitching consistently (slow and steady) over the 12 months instead of shutting it down for months at a time and then ramping back up. My DD has been pitching for almost 10 years, with zero injuries (knock on wood) and I do attribute that to good mechanics but probably more to the routine I mentioned above.