Now that the vacations have just started and there's a still month to go, do not take stress so much in advance. Enjoy the vacation and let him enjoy the time that is not strictly bound by the clock. And when there's a week or so for the school to re-open you can begin setting his routine by putting him to bed on the set time. And when he would sleep by say 9 or 10, he would wake up on time as well.
This is something all parents go through when the vacations start. Even my son's school re-opened today and to be honest I was equally tensed as how he going to be back to his routine, but he did, and yours too will.
Just don't stress so much in advance, and enjoy your extended timing of sleep as well.