My advice is to do two middles and the adjacent window. There is not a significant divider on the DL A330 between the two middle seats (i.e. you can still see each other, pass things back and forth, etc. although you cannot physically get into one seat from the other). The parent in the other middle is responsible for feeding, entertaining, etc. (they can lean forward a bit to see the the other middle) while the parent in the window is responsible for anything that requires aisle access or significant hands-on.

Also be aware of carseat restrictions in certain D1 cabins if you're planning to use a carseat.