Here's something you may not have considered. As a parent of twin babies, if you and your spouse want to fly somewhere with them as lap infants, you will not be allowed to sit with your spouse.
At first this makes no sense, but the problem is that each set of seats on an aircraft only has one extra oxygen mask, and your bundles of joy require two.
This came up in a discussion yesterday with a colleague who was already trying to juggle a combined work/pleasure trip with all the attendant seating and booking issues. He didn't need this added headache, but as a parent of twins, he's getting used to it.