FWIW, we usually go with bulkheads with our little ones---no chances of kicking/pulling on the seats in front, and there is typically more room to roam since there is zero chance of anyone reclining into you. Also, at least in the DL case, close access to the lavs and the front galley, both of which are frequent visits for us.

Regarding seats, I would suggest getting an aisle and window, even if they are not adjacent. (DL F on a 757 is 2-2.) Seat your kid in the window. The person in the aisle next to your kid will gladly swap for your aisle.