We traveled many times with the twins under the age of two, and we always purchased (typically with miles) all three seats in a row. The extra space of having the empty middle seat or cramming them both against the wall with my wife and I in the middle and aisle is a godsend. We always snagged the bulkhead for more crawling around room as well.

I was blissfully GS when they were very little would often get all of us upgraded, and the same oxygen mask issue holds in first class too. Three masks for two seats, so you have to split apart in first as well.

Now with three kids, we are just screwed.