On a coast to coast trip, there will be times when you miss a lot in those 300 miles and other times when there won't be anything for many, many miles. If it were me, I'd make a list of all the things I'd like to see and plan the trip around that.
I'm a big fan of getting the driving out of the way all at once, but that's usually because we don't plan to stop and smell the roses. I'd much rather drive 800 to 1000 miles in one shot and get there. However, your trip is more about the journey and all the stops along it, then the final destination. I would plan the heck out of it, but I wouldn't get all worked up if plans changed.
-Michael