If you have a GPS, rely on it, but make back-up plans just in case. Write down all your addresses before you leave, just in case your GPS doesn't find them. Better yet, program them in ahead of time. But bring the written ones, too. Over the years I have had to replace two failed GPS's, and of course this only happens when I am traveling.
If you don't have a GPS, but have a smart phone, and a data plan, utilize that feature. Bring all your chargers and so forth so that it works thorughout your trip. In fact, make sure you have all necessary adapters and connecting cables for every device your bring along on this trip.
Bring your camera and take lots of pictures! Bring extra batteries or the charger for the camera. Bring a back-up battery or a back-up camera (and it's back-up batteries). Bring an extra SD card for your camera, or make sure you start out with an empty one with as much space on it as you can afford. Take pictures of the location you are visiting as you enter. This is a reference to help you remember what the following photos are from. Especially when you are going to see so much you have never seen before.
Pack a cooler with frozen water bottles, which you can drink as they melt (some may take a day or two, depending on circumstances). Prepare nutritious or comfort foods ahead of time to eat when you stop at rest areas. Include fruit or other favorites that will help keep you energized for the trip. Bring tea bags or other caffeinated drink if you so indulge, to help you along the way. You can make tea in a cold bottle of water, same for coffee if you like instant or coffee bags (like tea bags.) Other coffee options are concentrated coffee that you add water too (comes as a liquid in a small bottle). Sometimes long drives, especially in the heat can make one drowsy, so watch out for that and take precautions.
Short power naps at a rest area (15 minutes) with a timer set, in my car (with a small pillow) helped me get across the country when I moved from California to Illinois in 2005. I used a kitchen timer and a small baby size pillow.
If you are planning on crossing the Golden Gate Bridge, stop at the first Rest Area as you come off the bridge going North. The photo ops are great at that Rest Area. It's huge and has tons of parking and rest rooms, of course. You don't have to go that route, but if it's on your bucket list...
If you are able, avoid driving West in the late afternoon. Driving into the sun can be very hard on the eyes, causing eyestrain and contributing to fatigue. If you are able and night driving doesn't bother you, drive at night. I don't like night driving anymore, but when I was young I preferred driving at night. When possible, try not to drive through major cities during rush hour traffic, but that can be pretty hard to avoid in California, where it seem 'rush hour' lasts about 3 or 4 hours twice a day in some larger metropolitan areas.
Check you oil and other auto fluids when the car is cold, such as before you start in the morning, or after it sat cooling down while you ate your meal. Carry a couple of extra quarts of oil in your car to use as needed. Motor oil at gas stations tends to be overpriced, so buy it ahead of time to avoid the higher prices. Make sure your washer fluid is filled before you start the trip. Keep a roll of paper towels in the trunk, for three reasons: use for cleaning the dip-stick when you check the oil, use for cleaning windows (when gas stations run out of paper towels), and to use as napkins when you stop to eat at rest areas.
If you take I-5, you are bound to have more dead bugs on your windows than most other freeways. I don't know why, but I get far more bugs on my windshield on I-5 than other highways in California. So stop and clean them frequently at gas stations. Not only for better visibility, but you might just want to take a photograph through a window.
Pick up hotel discount books at rest areas and truck stops if you are so inclined. Some times the prices are pretty good.v Another fun thing is a map of the US from Cracker Barrel. I used to stop there to eat with my granddaughter on our roadtrips & we'd pick up a map and with a highlighter, track our trip. Aside from have most of the major highways on the map, it also shows all the Cracker Barrel Restaurants along the way as well.
I hope you have a wonderful time. Redwood trees are fabulous. I grew up in a redwood forest in Northern California. We had a burned-out redwood on the property that my brother and I used to sit in/under like a fort.
bet you would not make 3 weeks and 5k miles on the back of a Harley and never getting on a freeway once out of Las Vegas! I agree flying is not cheating it gives you more time to enjoy the area. You have a great time
