The air conditioner will leak when the house is full of company. (poor Shirley)
People will be late.
We will forget several somethings we meant to bring along.
Baby drool will be on our shoulders.
At least one baby will break out in a rash because of the grass outside.
When we finally gather the whole family for the big group picture, at least one baby will start to fuss and cry and turn red.
Yes, if anything can go wrong, it will. But it will also come out right in the end.
The pictures will be beautiful.
The family will have so much fun together in the end, they won't remember the stress in the beginning. And eventually, we will forget how hard it was to organize, and we will be crazy enough to do it all again.