A huge thank you to everyone who commented. I was able to find a magical deal from a
travel agent and for a difference of $1900 instead of $2800 we decided to go with 8 nights at Poly!
A few thoughts in our decision-making that may help others in a similar situation:
1. The room size. We need a little more elbow room with 3 adults.
2. Monorail. My boys LOVE the monorail and they said they wanted to be close to it so they could just ride it for fun (they did that for hours on a rainy day on our last trip).
3. On-site character dining. We use the dining plan primarily for the character dining experiences. Having one on-site is a huge bonus for us.
4. The cost difference is about one day of work for me. I figured one day in the office is worth the extra comfort and convenience for my family (a thank you to the fellow consultant who helped break it down in billable hour terms)

5. Babsy's comment:
"Comfortable accommodations and good sleep are essential to a good trip for us." That sealed the deal. SO TRUE!
Again, thank you all for the great advice and opinions. It was great appreciated!