Once you get to FW, you'll go through the security gate, park your car and walk over to the Outpost Depot. From there you'll use internal Fort bus system to get to Crockett's Tavern, where the sleigh rides board. The internal buses run every 10 minutes or so, they all take different routes through the Fort and will make stops, but will arrive at the Marina/Crockett's area. You can check out a map to see the routes - yellow, orange, purple.
Assuming you stay at AK until closing, get to your car, and drive over to FW, then get the bus to your destination there, I'd say you need to allow at least an hour from the time you get to your car.
You will be amazed at the decorations on some of the campsites, and you'll only be seeing a fraction of them! A favorite activity of those of us who camp during the holidays, is taking a golf cart and "looping" to see the magnificant displays throughout.
Enjoy!