We are planning a trip SLC to visit family in August 2011 and will make a "detour" to
Disneyland 
rotfl2: what my husband looked like when I called it a detour) for our kids first Disney experience (currently ages 4,3,2, and 1).
We are also planning a September 2012 trip to WDW hopefully staying in the BLT or BCV.
We have done several rode trips since we have been married including driving from Baltimore to San Diego when I was six months pregnant (never again

) we have driven with a 2.5 yr old, a 15 month old, and a 5 month old to SLC from Tulsa. We have also driven with a 4, 2, 1, and 8 month old from Tulsa to Baltimore.
We drive straight through. We leave around bed time and it generally takes us about 30 hours (either way) when you include stops at play lands to help the kids get the wiggles out.
It's been awful! Especially since we don't have a van or large SUV (we have a jeep cherokee with an after market 3rd row seat). At Christmas this year we had to use a roof top carrier to make it home with the presents and everything else we accumulated.
My husband loves rode trips and hates all the waiting associated with flying (plus he used to fly every other month as a teenager so he got sick of it).
Right now we are planning on driving for both trips (though renting a van to make the trip easier, unless we end up buying a van before then). We figure $1500 total (probably less when you get down to it) for gas, food, van rental, tolls, etc.
I've been pricing flights around the same time I want to fly, and it will cost us around $2200 for all of us to fly (no vehicle rental, no food included). Because of where we live there is pretty much never a direct flight anywhere. We would have to drive 4 hours to catch a direct flight.
However if we could get the cost of the flights down to around $1500 then we will fly. (we are leaning towards BLT so we can walk to MK which is where we will spend the majority of our time) So we are saving money and will watch airfare up until the day we are leaving for our trip and if we can get airfare comparable to driving for us then we will fly.
Right now we really wish we stilled lived in the DC area so we could get all these awesome deals to Orlando! Saw some decent deals out of Dallas but I don't know if we want to drive 4 hours for a flight.