I'd also vote for 2+2 and the divide/conquer. Esp. since I usually end up on the 3 side and it's hard work to simultaneously entertain the preschooler and feed the baby/keep him from kicking the seatback at the same time. In theory the +1 can try and entertain from across the aisle but that's not always feasible (mealtimes, aisle traffic, etc.)

On the positive side the +1 parent has a pretty relaxing time.... And if the stars align, and the baby sleeps and preschooler gets engrossed in a DVD/videogame/toy, you both might actually get to relax with a drink and read your book. But don't count on it.

p.s. Another reason for 2+2: put the seatback kicker (if you have one) behind another in your own party so you can: a) limit the recline, and b) not feel guilty about annoying an innocent stranger.