Michael--
I have just done that exact drive last Friday. It is +/- 470 miles, depending on how you parcel it up... However, the pace on that road, the generally uphill trend, the curves, the traffic, etc mean that expected driving times can't simply be calculated at 55-65 mph. It took us about 9 hours of just driving, with some stops scattered in...
A couple of thoughts:
1) Consider minimizing the amount you will be driving on Monday, July 4th, particularly that afternoon. I wonder if that, being the last day of the holiday weekend, will be a complicated day to be driving around...
2) Definitely take the spur off 101 that is called "The Avenue of the Giants". It is about 40 miles, and roughly parallels 101, and has waysides, hiking trails, a visitors' center, etc., dotted along it... One can get a pretty good dose of the "redwood" experience in a single afternoon, unless you want to hike/camp, etc.
3) Ferndale is a pretty nice "Victorian" type northern California town to stop and look around, antique stores, etc....
4) Years ago, we stayed at the Benbow Inn, just off 101, and at that time it was highly thought of, with an excellent restaurant. I suspect that time may have taken a bit of a toll, but perhaps someone else here may confirm or deny...
5) Unless you are really averse to the whole wine-making scene, certainly consider at least some time in Sonoma, Healdsburg, Russian River area, so that you stay (more or less) on the 101 corridor. I very much like the Sonoma, Glen Ellen, Kenwood corridor as well as the wineries off River Rd. etc, near Santa Rosa. If you stay at the Sonoma Mission Inn, I think you can play the Sonoma Golf club, which was one of my favorites when I lived in the area.
6) There are a vast array of different lodging/restaurant options, but many of these are trendy and can come and go quickly, so local residents may be of more help, or AAA, etc.
7) The rocky profile of the northern Mendocino and up coastline of California/Oregon is truly spectacular, and I wouldn't pass up the time to walk along those beaches, if the weather is appropriate...
Good luck!