Hello-
We took our lo on two trips at age 4 mo and 6 mo, each a 6.5 hour drive. He did great. We bought a portable DVD player that mounted for his rear facing seat and lots of Baby Einstein movies. I also sat in the back and brought loads of toys and books, etc. We never had any real sleep issues, and used cribs the two resorts had supplied for us, but I agree with pp, bring a sheet, blanket and any other significant crib toy you have so it feels more like home. I didn't do this, but wish I did, if you can bring the bumpers from his crib, even better!
I realized he didn't care where he was as long as he had his mom and dad!
Oh, we also brought his exersaucer which helped a bunch! It collapsed to fit in the car, and was wonderful in the hotel room. I didn't have to leave him on the ground. We even brought it to the pool and he played for hours in it.
Call ahead to where you are staying, you may be surprised how much they have available for you,