Hi Sheree,
The only factor at all that would make me consider choosing 2 rooms at the
Caribbean Beach Resort over a room at the
Polynesian Resort would be the fact that you'd have 2 bathrooms to get ready in the morning. As a family of 7, and taking that into consideration, I would still pick the location and convenience of the Polynesian hands down. You can simply get up a little earlier to start the showers.
Caribbean Beach is a large, expansive Resort that is located a distance away from all of the Parks. You will spend quite a bit of time on the Disney buses. On the other hand, the Polynesian is a monorail ride away from the Magic Kingdom and Epcot. The daybed at the Poly will be fine for either your 10 year old or your 2 year old. If you are like my family, It's not like you will spend a lot of time in your room anyway. You'll go there for to sleep, turn around and head out to the Parks again.
To me, it is all about location, location, location. Based on that, the Polynesian trumps the Caribbean Beach every time and it's worth it to have a little less space in the room.
Hope this helps and that you have a wonderful vacation,
Kaylene