What an interesting idea...I am surprised I did not think about that when my children were that young.

I think it will work, be nice to the flight attendants as to them claim that people cannot move beween cabins....but they can. My wife had switched from coach to BC during the flight (once) and I think most FAs are understanding.

Keep in mind that if you do not buy a seat, then the infant has to buy space at 10% of where the parents are ticketed. I always bought a seat, and I was always up front, so there were sometimes where the 10% was a big number...even if the seat was an AAward set.

My I suggest that after you get some responses here you have the moderator move this to the travel with Children forum.