We are driving clear across the country - 3,000 miles - which we've done several times with our kids (almost 4 and almost 2). This is what we bring:
DVD player - you will LOVE it! It really helps to keep them entertained
Music - if they like music, buy a couple of CDs of kids music to play (our kids love this, us - not so much!)
Dollar store toys - I just went to the dollar store and bought some new little toys for them, along with some new books. New stuff is great - it will keep them entertained. Then, wrap them up in wrapping paper. Put them in a bag and let them choose and unwrap as needed - they love this!
Trays - if they are old enough to color, buy those trays that are usually for eating in bed. Ours fits right over the car seat and DD3 can draw and color while we drive. If they are older, a clipboard will also work.
Glowsticks - our $ store sells packs of glow bracelets and sticks. We give these to our kids at night - really amuses them!
Mini magnadoodles - we have 5 of them! Both our kids love to draw on them in the car
Snacks - we bring sippy cups and easy-to-eat snacks. Your grocery store should have those little snack packs of goldfish crackers, teddy grahams, etc. If you are near a Babies R Us, they have those little snack cups with the flip lids to keep things from spilling
If your kids are old enough, try some of these printable games:
http://travelwithkids.about.com/od/printgames/
Plan to stop every 3 hours. We always travel with a cooler filled with stuff for lunches and stop at rest areas for lunch, allowing the kids to run arouind. I know a lot of people like the McDonalds playlands for those, but we try to keep our kids away from those - too many germs, and we don't want them sick on our vacation!
Good luck - I envy your 7 hour drive! Mine will be 34 hours
