Middle school and below can suck it up and go anyway.
High Schooler can stay up, but, don't whine to me about how early it is when i wake you up.
Under 5 we will work around it and try and coax them to bed.
If he is old enough, tell him he can have some quiet time in his room until he feels sleepy, get some books maybe crayons and paper and let him go at it. As long as he stays in his room and is quiet, then after about 30 min check on him and try to get him to sleep.