When we go on long drives my kids like to play an alphabet game. (I some times play it when the kids aren't even along!!). Starting with the letter "A" you find a road sign or store front or liscence plate with the letter "A". Then move onto the letter"B" etc. etc. The letter must be the first letter in the word you see. Some letter are more difficult to find. "Q" look for a Dairy Queen. "U" look for a U-Haul truck. "X" some Ford trucks use XLT on them. "Z" can usually only be found on liscense plates.
We always have a lot of fun playing this game, and it really helps the time fly by.
We have also played "car color". Each child picks a color before you begin driving and they get one point for each car of that color that you see. The cars must be driving. (parking lots and car dealerships do not count). Be careful. Some colors can be questionable and may cause arguements. Pick mommy or daddy as the judge.
Have a great and safe trip. Hope these game suggestions help.