Welcome to FT. I would suggest you search for "Seating Queries: First BA" and the FT thread on this will be the top hit (sorry I don't know how to link on here).
I asked a similar question the other week as we have our first First next year also. I have plumped for 4E and F so that we can sit next to each other and enjoy the First experience. I didn't want to be shouting across the cain from 2A to 2k.