KLUA is one of the prettiest airports around. A throwback to the golden age of flight. And the flight through the mountains is really pretty. The area just had snow, so the flight will be absolutely gorgeous. I personally find the caverns ok, but not great. A little too much of a tourist trap for my taste. But i'm definitely in the minority as most people enjoy the caverns. Since you will be flying near or even in the SFRA, don't forget to take the online course before you go.
I know you were asking for ideas around Christmas, but if you find a particularly warm day, check out Ocean City, MD (KOXB). It is a short drive from the airport to Assateague Island National Seashore. Beside the obvious spend the day at the beach, there is also crabbing, canoeing, nature trails, and looking at wild ponies. You don't really need to go in the summer, but it is an outdoor activity. OXB has inexpensive gas and rental cars are usually $25/day if you negotiate. Maybe less during the off-season. They charge a parking fee of $6/day but will wave the fee for 10 gallons of full service gas ... which is exactly $6 more than the self-service price. Even at full serve, the low cost of gas makes the parking a non-issue.
If you are interested in skiing/snow tubing you can check out Sky Bryce (VG18) which is just west of KLUA. But check your aircraft performance specs as the field is about 2200 ft long and surrounded by trees. If you can get in/out the field is a short walk to the ski resort.
Some other ideas:
KIAD ... Udvar Hazy Smithsonian Air-Space museum .. See the Space Shuttle
KWWD ... Wildwood/Cape May
Have fun!
