This Christmas was my three month old DD's first.

My MIL and her boyfriend arrived at our home shortly before dinner on Christmas Eve and stayed until about 10am Christmas Day.
Before going to bed Christmas Eve, we discussed the next morning--we told them that DD usually gets up around 7am, and so we would open presents then. We told them that DD has a very short window when she wakes up in the morning before she's ready for a power nap (an hour if we're lucky, including her bottle). DD's room is right next to the guest room and they assured us they'd hear her get up and we'd do presents then.
Christmas morning comes, DD wakes us up at 6:45. We let her take her time waking up in her crib (unswaddle, etc.) before heading down to check out the tree. We wait, and we wait, and we wait...DH starts a pot of coffee. Keep waiting. At this point I'm frustrated because we have a short window and it's diminishing...I head up to use the restroom in our bedroom and hear MIL and her boyfriend chatting. So, they're definitely awake. I tell DH and he and the dog head up to find out what the plan is.
MIL's response? 'Oh, I was waiting to hear the coffeepot beep.'
We had to rush present opening and had a fussy DD for about half of presents (which wasn't a ton). Not the Christmas morning my little family wanted.
What would you do in the future? Knock on the door and wake them when DD gets up (even if you know they've heard her)? Open presents when we want and if folks miss out, too bad?
Not a big blip on an otherwise awesome first Christmas, but her selfish attitude continues to irk!