What is a good bedtime for a 4 year old and a 2 year old?

2 yr olds need 10.5 to 12 hrs of sleep 4 yr olds need 10 to 12 hrs of sleep.Between 6:30 and 7:30 would be an ideal bed time for then,since they wake up so early in the morning.My son is 8 yrs old and if he doesn't get at least 9.5 to 10 hrs of sleep he tends to get a little cranky.