Hi April!
Welcome to the Disney Parks Moms Panel! December is a wonderful time to visit Walt Disney World Resort. Not only will everything be beautifully decorated, most Disney Deluxe Resorts will smell like the holiday season thanks to their
larger-than-life gingerbread displays!
I was extremely lucky to stay at Disney's Grand Floridian Resort & Spa last December. You're in for a real treat, April! I can definitely relate to wanting a quiet guest room, especially after a few long Disney Days. I was in a pool-view room in the Big Pine building, and even being so close to the hot tub I didn't hear a thing unless I was on the balcony.
I honestly don't think you could go wrong with either building. My personal input would be that
when looking at a map of Disney's Grand Floridian Resort & Spa, the pool areas don't show their perimeter fences. The entrance to the Boca Chica building is right next to an entrance gate to the Courtyard Pool area. Walking through the pool area to get to the main building or to the Gasparilla Island Grill is faster than walking around the entire pool area; however the pool is not open 24/7, so you'll be in for a slightly longer walk from Boca Chica than from the Big Pine Key building.
One more personal opinion - my friend and fellow
Disney Parks Moms Panelist Missy F. had a lagoon view room also in the Big Pine Key building. The lagoon side faces Disney's Wedding Pavilion, and she was able to see magical Happily Ever Afters throughout her entire stay!
I hope this helped, April, and We'll See You Real Soon!
~Kristen