That is quite a drive! We drive at night as much as possible because it is easier for us. My girls are 5, 3 & 1 and if they can sleep on the way that is a good thing!
Hit the dollar store! I get Disney themed stickers, crayons, coloring books, folders, board books and even snacks! (also a great place to grab cheap rain ponchos and glow sticks for use in the parks) I also snag handheld toys, games, and bubble stuff.
Then I visit
www.themouseforless.com - on the left you'll see a category called downloads which I LOVE! They have Disney trivia, search-a-word puzzles, park tips, etc. I make each family member a folder with these types of things in it. I've also made up car bingo games with things the kids can easily identify. I'm no artist so I printed out clip art and glued them to a piece of cardstock to make the game board. These were a huge hit with my kids and I'll make several more the next time! They use Disney stickers to cover the spaces they've found.
I also get new Disney jammies for the trip; we get them all dressed for 'bed' and let them watch a movie before they fall asleep. We use a DVD player in the van or play movies on a laptop computer. If you don't have either, I highly recommend buying a portable DVD player. The prices have come way down and they are worth their weight in gold on a car trip! We also pack every Disney CD we own and have a sing-along, and play Disney games too (like A-Z, naming a Disney character for every letter).
And again, I'm out of room before I'm out of ideas! Maybe I should quit talking (typing) so much!
For the parade viewing, there aren't any bad spots. I think the biggest advantage you can get is to watch from the left side of the street. Maybe it's because most people are right-handed, but it seems the right side is always more crowded than the left.