well in honesty on xmas morning I dont rush to get dressed and the house ready for visitors, its very relaxed, its the one day where you can relax without having visitors banging on the door.
I think you should cut him some slack in that respect, 11:30 may seem early to some people and late to others
when people have kids then yes, sister,mum and dad do become more extended family as his wife and children become more immediate family, its the circle of life, my sister has a husband and 2 children, she is spending xmas day with them as they are her immediate family now, as I am with mine.
can you not arrange to visit at a different time, Im sure he would like to see you without the stress of getting the house sorted and getting dressed up?