I had 4 on the 757, which was a challenge as well. Mine were smaller kids, so I put the smallest in B directly behind the 2nd Smallest (just in case there was a slammed tray or two.) My wife took C with one, and I took C with the other. I had power, and when they needed it. I handed them the cord between their seats. No problem at all.

No one was in A, on one direction, but there was on the way back. THey didn't mind at all though, becuase both were very well behaved.

Family vacation is one of the few times, that I don't get an exit row.