Judging by the seat map, I am guessing your flight is still several months out. Therefore, since you are using reward tickets with very little money out of pocket, I’d spend the $204 to select row 12, seats JKL. That way you have certainty that you are all together for the 10 hour flight and you are near the middle of the plane which tends to be a little quieter (so easier on the toddler’s ears). While I hate the idea of paying for seats (fortunately I’m OWE so I’m able to mostly avoid it), when I fly other airlines I will pay for seats when I’m not willing to risk getting a crappy seat at check in.