i think it is a good compromise to leave at half time.
in the old days.....(ha ha) we used to run around the street from 7am to 7pm as kids by ourselves on school holidays.
i'm sure a few hours would be fine.
my son is nearly 10 and he also asks if he can have a lolly, specifically comes down to the shed if we are down there! i think you know your children and what their maturity levels are.