K.D.
Kids usually do amazingly well on road trips. We traveled 120,000 miles in the car, leaving when baby #1 had just turned 3, baby #2 was 15 days, and we added another one on the way. I don't miss that job so much. :)
We did special toys for in the car -- Magna Doodles, DVDs with a portable player, Leapster or Leap Pad, etc. Crayons and lots of coloring books, or magnet books go a long way. One time when we were desperate, we gave our son a napkin to shred. That entertained him for a long time. It also took a long time to clean up. :)
Healthy snacks do well. We also would try to eat in the car when possible. Chicken nuggets worked well for that. You can also do fruit that way.
Since it's not a long trip, and could be done in one shot, driving through the night is a great option. We did that many times. The kids sleep well most of the time, as long as you keep moving.
If you do it during the day, you need to plan on about a 14 hours of driving time for a 10 hour drive. You'll need breaks for the little one to get out and run. We tried as much as possible to combine stops. Everyone goes to the bathroom/gets a diaper, gets new toys, old toys that have been dropped get cleaned up, get new snacks, get a few minutes to get out and run, get gas. It makes for a long stop, but overall we seemed to save time by not having to stop so often.
You will need to change diapers more often than you would at home as diapers don't absorb as much when the baby is sitting on them in the same position the whole time. The back of the diaper doesn't get used other than for dirty diapers. If you double wrap dirty diapers, you can leave them in the trash cans without making the trash stink. I love piddle pads, because when there is a leak, the car seat doesn't get dirty. Babies 'R Us has some really nice ones for about $7, I think, or you can get disposable ones. The disposable ones don't work as well as they move around a lot, so you really have to use two at a time.
I would recommend taking a favorite blanket or lovey of some kind, and of course favorite toys that wouldn't be too annoying. Books and a ball to chase at breaks are good, too.
I hope you have a great time, and baby does well. Even with all the preparation, it doesn't always work. Our last road trip should have been 15 hours, but took 21 instead, but coming back was an easy 15. Who knows why it works sometimes and not others. Kids do seem to figure out the plan, though, and do quite well on long trips, even when short ones are a pain. GL!