Hey Shannon! I love staying on the monorail as well, and with the ages of your children, you will love it even more. If a deluxe resort is in your budget then honestly you can't go wrong with the Contemporary, POLY or GF. My suggestion to you would be to go to
www.disneyworld.com and check out each of these resorts on line. There are great pictures of not only each resort's room but also the lobby area and pools. And honestly I enjoy staying at all three. My personal preference is the Poly, but mainly because it's where my girls enjoy staying.
As far as crowds, it ranges so in December, but honestly I think you are going to do a lot better with crowds the week before rather than the week after. According to many guide books this is considered to be one of the least crowded times of the year to visit, but again you just never know for sure. If you find yourself navigating through crowds, just smile and say "It's the holidays and we are at WDW."
Thanks for the great question and for coming to the Mom's Panel.