We're going to crunch the numbers for our next trip, but so far it has been in our favor to drive. We find an inexpensive chain hotel for the one night each way, and we often eat a picnic lunch on the way there.
Once our kids get older and we don't have to stop so much, we might be able to make it in one day. Google says our total driving time is just over 12 hours, but with littles, it takes more like 18-21. With a flight, we would have to take a 2 hour drive to Houston, get there extra early and wait, then the flight itself, then wait for magic express once the plane lands. I can see it taking a good 8 hours when you combine all that.
Plus, flying is just uncomfortable for me. We have a minivan, so we can pack just about whatever we want, stretch out, watch movies, etc. The kids bring small toys and games, and they travel well since we have done this for so long.
Older child has asked us if we can take a trip in an airplane one day. Since we often travel in our camper (and prefer it), the plane isn't really conducive, but we probably will one day just so the kids can have the experience. (I don't think they're missing much. lol)