"babies that sleep alot at 13 months of age..." LOL!!

Maybe if you are lucky!! Even when we took our 7mo, she didn't even sleep but maybe her normal 1 hour or so at the park! Hopefully you will be one of the lucky ones with a 'calm' child, however, realize that that sweet little baby will also be walking during that time! They will be so excited about this new feat, that they won't want to stop at all!
Please don't let me overlook a hearty "CONGRATS!!!" to you!!! Having a child is the most wonderful thing in the world.
Regarding the dinner seating, I would just go with the flow. Quite honestly, I (my preference only!!) would try to get the 2nd seating, because I would rather my child be fully awake during the show & be able to enjoy it. Then, if they get tired during dinner, maybe you would get lucky & be able to enjoy a meal with the 2 of you, while baby naps! (You can take strollers into the dining room with you! We did!)
Once you get closer to the date, and find that you would rather have a different seating, you shouldn't have a problem changing it as soon as you board.
Good luck!!
