I have 4 kids, 6, 5 and 3, and a 1 year old. The one year old is about 6:30, the 3 year old is not far after that. The older two during the school year is no later than 7:30, and usually they all go down at the same time. By seven.
Now, lucky for us, we have kids, that sleep 12 hours at night (even the baby now), and it does not matter what 12 hours, they just sleep a solid 12 hours.
So, during the summer, my kids go to bed probably around dark (nine), the baby earlier. But, they all sleep until 9.
If we are on vacation, and they are up until 11 at night, they will sleep until 11 in the morning, sometimes it is just a solid 10 hours. (but usually the 12) Even the baby.
We just spent a week in cleveland, and lancaster. We were not even waking up until 11 in the morning, pretty much every morning. I don't stress so much during the summer, and vacations, those are fun times, they go to bed when we get there. They are not crabby, and don't whine. We had a ball closing the pool for a week straight at 11 while on vacation!