D.H.
I would book seats 2 & 2, not you with the two kids in one row. I have 2.5 year old twins and we did that once (don't remember the airline) and we were told once we boarded that 2 young children could not be in a row together with one adult because they cannot put their oxygen masks on themselves. This may have been just an uppity flight attendant but they had to move a bunch of people around so we were each with one child and we ended up 20 rows apart. That made it very difficult to access the one diaper bag with all the snacks, toys, diapers etc. Now we always book a window and and middle seat in rows next to each other and always pack two different bags.
Have fun!