I've been spending Christmas at Big Bend for 5 or 6 years. If you get there before Christmas you generally won't have a problem getting a site. While Chisos Basin is the best place for hiking, it it a bit difficult getting into with anything longer than about 24'. And there are few good RV camping spots - most are not level. A few years ago they turned about half of the good spots into no-generator spots. There are no hookups in the Basin and only about a dozen in the parking lot at the Village. I think they are commercial. There are lots of excellent spots in the NP RV area at the Village, all level and most are shaded but no hookups. There is a little hiking within walking distance of the RV area.
I'll most likely be at the Village this Chirstmas with my little Class B and my Jeep. If you're there at the same time stop by and say Hi.
Oh, I've got quite a few pictures from past trips.
Bob's travel log-bob