We drive from PA to Hilton Head every summer. I've driven solo with 3 kids a couple times.
I pack two coolers: a lunchbox size for me in the front and a bigger one for the kids. I pack NO flavored drinks, only water. The kids drink to thirst instead of chugging juice boxes. Snacks are generally pretzels, grapes, cheese sticks, dried fruit and things that are healthier. Sometimes we have fast food, sometimes sandwiches. My emergency treat are the orange mint lifesavers. We all love them.
We burn cds and listen to a mix of music. Some that they like, some that I like. One year, they learned most of the words to American Pie. We always play the alphabet game and I am (so far) unbeatable. My kids ALL love Mad Libs. The books are kind of hard to find, but you can also find them on the internet. One of my children can read in the van with no troubles, but the others would rather read magazines or the Guinness book of world records. I don't buy many books as we usually use the library, but I always buy some for the vacation (new and used). It's one of our treats.
Because my kids are getting older, I tend to set a bathroom policy at each stop. That means I decide if children can use the facilities solo (with me at the door). When I'm driving solo I generally don't stop at rest areas, I'll go to a restaurant or gas station. The smaller bathrooms are easy for me to manage.
My kids LOVE staying in hotels, so that doesn't present any problems for us. They especially enjoy being able to watch tv in bed.
I also like to leave early and then stop for breakfast. This isn't for everyone, though...I have had almost 12 hours driving alone. Most importantly, though, is to make sure I stay rested. It's only me so I make sure I get enough sleep and stop/start when I want.
Have a great trip!