Hi Elizabeth,
You have some lovely options for your stay at Walt Disney World! Both
Disney's Polynesian Resort and
Disney's Wilderness Lodge are each so beautiful in their own way. I am going to suggest that you stay at Disney's Polynesian Resort. Let me explain why.
First, you say that you've always wanted to stay at Disney's Polynesian Resort. I think that in that case, you should absolutely go for it! My family and I so love experiencing different resorts. Returning to the same resort again and again is special in its own way; however, I also think that it's great to get out and experience a new resort. This trip seems like an especially good one to do this on because you are celebrating such great occasions - your 20th anniversary and your daughter's 16th birthday! I suggest making it a special trip and staying at Disney's Polynesian Resort.
I also really love the theme at Disney's Polynesian Resort. The South Pacific feel is so lush and beautiful. Also, you just can't beat that monorail access! Getting to both Magic Kingdom Park and Epcot is so easy with monorail access right outside of your door.
So, Elizabeth, that's my opinion. I think go for it - celebrate at Disney's Polynesian Resort! I hope that this helps with your decision. Please come back and ask if you have any further questions!