We have driven straight through during the night from Ohio the last 3 trips. Yes, you are pretty tired when you arrive - that's why the first day is usually pretty low-key. We switch off drivers and the one rests while the other drives. The first trip ds was 6 months old; next trip he was 3.5 and dd was almost 1; last trip ds was 5.5 and dd was almost 3 - they never woke up when we stopped at rest areas, gas stations, etc. On the way home last time ds slept from the FL Turnpike until we reached Cincinnati. My kids can sleep through anything - they don't need dark or quiet.
This trip we (me, dh, ds8 and dd5) are leaving very early in the am and driving until 8-9 and then stopping for the night. The rest of our group (dd25, my cousin, her dh and children - ds9, ds5, dd4 and dd2) will be flying - our goal is to meet them around noon.
We drove in March with DD2 and DS6 months. It was a nightmare of mythic proportions, and I booked our flight for our December trip the day we returned from driving. LOL. Maybe we'll try again in 15 years.

We got airfare for all 7 of us for 950. Now all we need is to save a little spending money. We will unload some more stuff on ebay and maybe even have a yard sale. Thanks for all of the help.