The aft balconies are larger and deeper than those along the sides of the ship. But if you want huge, the cabins on the ends (like 1688) have balconies as large as the rooms themselves. We had one of those cabins in 2004 on the Mariner. But your balcony will be quite good sized. Bear in mind that there is a good bit of ship structure aft of your balcony, so don't expect to look down and see water. You won't.
We had a fine cruise on the Mariner. Formal on RCCL is not as rigid as on some other lines. A suit or sport coat for men. Cocktail dresses for the ladies. These seem to be the norm. Not many people dress for the theme nights. I have always found it ironic that RCCL says blue jeans are not allowed in the dining room for dinner service, yet they have a western theme night. I wear them anyway and have never had a problem. I am not alone either.
I can't tell you about the kids moving around in the programs. I think they are more liberal with older kids during the day, but I can't say with the younger ones. The youth staff knows how old every kid is - they get printouts before the cruise even starts - so you can't really sneak something by them. Maybe someone else has some experience in this area.