L.C.
My children were in bed at 7 until 3rd grade when we moved it to 8. In late 5th grade we moved it to 9. Once they hit high school, they went to bed at 10, and still usually go to bed around then if they can.
His kids are his responsibility, but a uniform set of bed times would work so much better. My husband worked late sometimes and I just told him that keeping the children up later for him was being selfish on his part. He adjusted his schedule and things ran much smoother. If that isn't possible, then, he can get quality time instead of quantity time. Is there a way for them to be ready for bed before he gets home? Then he can do dinner, stories and bed... I did that a lot if my husband was going to be late. He could still do stories and tuck them in - even if he didn't get to do the whole routine, he got the important parts.
Good Luck!