Make sure you have your CELL phone number on the id tag or microchip.
We went camping once (puppy was a week old) and realized that the tag with our house number wouldn't help much if we weren't home! Duh!
Take a doggy first aid kit, stuff like you might normally have around the house/barn you won't have on the road. Also you might want to find out where the local emergency vet is for the town you will be staying in. My dog is car stupid, and gets hyper excited about trips, so potty breaks around cars scare the bejeebus out of me!
I fed my dog Gatorade on a long trip besides water. Once we got stuck behind a semi truck on a winding mountain road in August. What normally would have been a super-breezy 30 minute trip, ended up being a hot and sunny hour long trip! We tried Pedalite but she wouldn't drink it (I wouldn't either, it tastes like salt water) she prefers the plain, red punch flavor. You might want to carry something for the dog in the cooler if it could be any hot at all. Either her local water, or bottle water, or Gatorade if your dog will drink it.