That solution has worked for me in the past too!
I am hoping to keep my 20-month-old out of the living room level during the time the tree is up. I live in a split level home and usually he is not allowed loose on that level anyway. Once Christmas is over I think I'll have to break down and take the gates off. He does stairs well enough and I'm killing my knees climbing these gates!
As far as the birthday thing, I have one child born 12/27 and another born 1/15 so I can sympathize! DD thinks the whole week of Christmas is for her
since invariably when we are visiting, someone will stick a candle in the dessert and sing to her for her birthday. I usually have one family celebration for the 2 kids, around the first weekend of January. If they have a party for their friends, that's done after school resumes. As far as the gifts thing, YES, they get all their gifts in one shot. It's tough. When they were little I'd put stuff away and take it out later, but they're bigger now and I can't get away with that!