We have taken several long road trips since DD was born, and overall, they went much better than I had expected. We try to coordinate our leaving time with her normal nap time (or when she starts to get sleepy; she doesn't have much of a schedule).
I sit in the back with her while DH drives, and once she wakes up from her nap, I entertain her as long as I can (lots of peek-a-boo/me acting ridiculous keeps her smiling) until she gets fussy. Then we stop, DH fills up car, gets drinks, etc... while I nurse her. We usually walk around for a few minutes, change her diaper, and get back on the road. Repeat....
I don't bother pumping and offering bottles because she has never taken a bottle before, and I know that she wouldn't be satisfied without actually nursing (plus I don't have to worry about cleaning, pumping, temperature control, etc...)
Good luck! Enjoy the ride; take your time and stop to see things that you otherwise wouldn't stop for!
Me, wife to DH , SAHM to DD (4/26/09) and DS (4/9/11)