Your rule is perfectly reasonable and it promotes healthy eating. I think if I were you I would withhold sweets for the rest of today, not all week. Not as punishment, just the logical consequence- he has already had his treat this morning. It is gone. Tomorrow is a fresh start. Any way, that's my 2c. What everdecision you make, stick with it and don't second guess youself. There isn't just one "correct" way to handle this situation.