Hey Stacey!
I can tell you that one of my absolute favorite weeks to go is that first one you gave... the week right after Thanksgiving.
Seeing the Holiday decorations in Disney World is just magical! It seems like every inch of the Parks and Resorts receive special treatment during the Holiday season...it's not overkill, it's just feels special. My family loves it so much that we try to come during this week every year now.
Also, the crowd levels aren't too high during that week which is nice. During your first trip you'll want to be able to really look around and not worry about being rushed along in a crowd.
We enjoy the weather during that time of the year because we can wear jeans and tshirts layered with hoodies or cardigans for the cooler mornings and evenings. I still wear sandals all day, but my kids like to wear socks and sneakers.
My husband and I brought our little boy to Disney World before having our second child, too, and I treasure those memories. He's now 10 and remembers a lot of that vacation!
Have a wonderful, magical first Disney vacation!