Hi Adrienne! Nice to hear from you again! I'm so happy you were able to take advantage of the Free Dining offer for your trip, and of course, I think your idea of using the savings to upgrade your hotel is a fabulous one! In my opinion, the more luxurious the hotel, the better! You really can't go wrong with either the Contemporary or the Polynesian Resort! If you like the Wilderness Lodge, you'll really love the more spacious rooms at the Contemporary and the Polynesian, and the convenience of being on the monorail route can't be beat. Like you, I would probably lean toward the Polynesian too because of the great restaurants and the fun volcano pool. However, I seem to remember your trip is in December, and if you're there during a cold snap, you might prefer being inside at the Contemporary, rather than having to walk outside to your rooms at the Polynesian. Also, the Contemporary has recently updated, really bright and modern rooms that I prefer over the darker decor of the Poly.
At the Polynesian, the volcano pool is behind the main building, where the restaurants, arcade and monorail station are located. If you request a room close to the food, pool, and arcade, you'll be close to the monorail too. The monorail from the Polynesian takes you to the Magic Kingdom as well as to the Grand Floridian, Contemporary, and the Transportation and Ticket Center (TTC), where you can catch a monorail to Epcot. If you don't want to ride the monorail from the Polynesian to the TTC, you can also walk from the resort to the TTC to take a direct monorail to Epcot. If you were staying in the Tahiti or Rapa Nui longhouses, you could walk to the TTC in five to ten minutes; however, those longhouses aren't as close to the pool and main building where you want to be. From the other longhouses, it's easier and quicker to just take the Polynesian monorail to the TTC.
Hope this helps! Have a great time!