Make sure to budget time to get them a good long walk in the morning and evening, or find a dog park near the hotels. I'm assuming you won't always know the areas you stop in, so you want to make sure you still have daylight left. Drove from TX to CO and back this winter and my guy was fine, just slept in the back seat, although after 2 days, he was ready to be done. 
 Also, think about your meals etc. Lunch at mid day obviously requires a to-go meal or something, but breakfast and dinner can mean having to leave your dogs in the hotel. My dog gets anxious when left in a strange place and hotels have a lot of noise and stimulation. We really struggle to leave the hotel room once there because my guy will bark/howl, but only in a hotel.