As others have said: I've done A,A,A with a 2 year old before. Probably not fully recommended with kids so young and we now tend to travel as A A, (2x Windows + Middle Seat, whatever number it may be) on 1-2-1 layouts. I imagine with a 14 year old the preferential layout would be all windows, so nobody has to see each other (unless you really prefer the middle seats for the couple, I find them in general to be fairly poorly laid out and so we avoid).

PS: Outside of just BA - I seem to recall JAL double checking with us a fair bit on this config, and Qantas was annoying in that they once rearranged us between seat selection and check-in when we were in business (!), though not First. Sigh, first world problems. But overall, once you're out of economy no oneworld airline really seems to have a problem with whatever config you may choose.

(**In my response assume A is equivalent to K, so either window)