All our boys have done the exact same thing!!! We compromise though on the wake-up times during vaca. And I agree with both your parents to an extent.
All our kids are good students, involved in organizations and activities and all work hard during summer break too. They need to catch up on sleep during breaks.
Some days, I need them up earlier to help out with errands or drop me at work. (During vaca we are 5 adult people here sharing 3 cars.) And I tell them the day before so they can plan to go to bed appropriately. They have learned the hard way that staying up until 2 when mom needs you up at 8 really sucks.
Then other days, they sleep as much as they want to.
Our rule though for late nights: you cannot disturb the sleeping parents!!! If I go to bed at 10 and you wake me up later with your noise, not cool.
Then what we do with the HS Senior is 2 days before the end of break, we "encourage" him to get back closer to his school schedule so there is not so much jet lag effect on the first day back to school.