We have celebrated our anniversary at WDW on 2 occassions, but since ours falls in April and that usually means Easter pricing, we generally visit in Jan/Feb/Mar or Sep/Oct. Our 8th anniversary was actually our 2nd trip (2000) and we LOVED it! Seeing Wishes from California Grill was so romantic and we will never forget the moment. We were not at WL on that visit, but we have stayed there since, so allow me to give you my impression:
Wilderness Lodge is probably the best THEMED resort at WDW. It is a very secluded feel being surrounded by mature trees. There is a quietness accented by the sound of birds and crickets (not sure if they are real or part of the WDW illusion, but it is NICE). A stay at WL truly feels as if you are in the Northwest, and I have lived in Washington, Northern California and visited Oregon.
They also feature one of the finest Signature dining places (and one of THE most romantic) Aritist Point. Their Whispering Canyon is lively with great food for breakfast, lunch and dinner!
And in December you will be absolutely stunned at how lovely the decorations are, especially the HUGE tree in the lobby.
No, they are not on the monorail, but it is easily accessable by taking the boat over to Contemporary or Magic Kingdom!
From there you can catch the monorail to Epcot, or catch buses to other resorts off the monorail should you wish to do so (AKL to see the savanah animals or have dinner at Jiko?)
You can also do a monorail tour of Grand Floridian (maybe book her a nice massage here?) and the Polynesian (Spirit of Aloha dinner show or the always wonderful Ohana?).
The boats availalbe also take you to Ft. Wilderness - perhaps to catch a romantic evening carriage ride?
And while at Contemporary, perhaps another special dinner @ California Grill with Wishes viewing?
Or a fun breakfast at Chef Mickey's?
And don't forget the WAVE - amazing place features as much local produce, fish as possible and generally easy to get an ADR! Wonderfully relaxing decor' that features what my grand daughter called the 'blue room' just inside the entry.
The buses to AKL and HS are available frequently directly from this resort and they are seldom crowded.
I cannot imagine a more romantic place for an anniversary, especially considering your history with WDW. GF is nice, but DH and I find it is way out of our comfort zone - we are midwesterners as well (live down here in Wichita). We have stayed at Poly and enjoyed it for many reasons, but for the price and amenities, WL would be my HIGHEST recommendation for you.
One other thing you might consider - pay the difference and upgrade to Deluxe dining. You will get 3TS per day (can use for QS as well, but WHY when you don't have the kids along?) and it includes an appetizer as well!
DH and I like to do a 1TS for an early lunch, then do Signature dining in the evening. With 2 snacks allowed per day, this is plenty of food for us! In fact, for the last 3 nights of our September trip we are staying at BLT and adding the DxDP. We plan CG, Citricos, AP, Chef Mickey's, Coral Reef and WCC! That is 6 nice meals over 3 days and a total of12 snacks to fill in any gaps (morning danish from Main Street Bakery @ MK, fresh fruit & water @AK, pastry from Norway @ EP and Starring Rolls @ DS - you get the picture.) It will only cost you around $30 a day extra, but that is a BIG bang for your buck!
Sorry for such a long post, but I wanted to do my best to assist your decision. Wherever you end up going, you will be with your best friend and life-mate, so it will be a great trip!
