We're from northeast Indiana, so assume in your general neighborhood. In 2010, we did a three week loop to the Grand Canyon, Las Vegas, Bryce Canyon and Arches in Utah, then back home via I-70 over the mountains. Just this past summer, it was a three-week loop through the Grand Tetons, Yellowstone, and back home via the Black Hills. From our experience, three weeks was too little for the first, and just about right for the second. We decided that traveling with our fiver to California would be best left to retirement in a few years when we have no time limits.
Keep in mind that getting there should be half the fun. We travel to relax, and find that 300 to 350 miles per day is our sweet spot. Pull out every day at around 9:30 and pull in at around 4:00 or so in time to relax, enjoy a leisurely dinner, and check out the area if we feel like it.
As for reservations, no need for the overnight stops. If you have an iPad or smart phone, get the AllStays application which is great for finding campgrounds. If no iPad or smart phone, pick up a Woodalls campground guide. In the early afternoon, we'd see how much further we felt like driving, pick a campground for our destination that night, then call ahead and make a reservation. In most cases, reservations weren't needed, but having one takes one more thing off my mind.
If you will be stopping any one place for more than a couple of nights, and especially if hitting any of the National Parks, make your reservations as soon as possible, and now is not too soon! If you're wanting to stay inside the National Parks, I recommend you call rather than reserve over the web. In our case, I'd made an online reservation in December for five nights in Yellowstone's Grant Village campground. When I hadn't received a confirmation after a few weeks, I called them up. Good news was that I did have a reservation. Bad news was that the site I'd reserved wouldn't fit our rig. The person that I had on the phone was extremely friendly and helpful, and with some effort, was able to fit us in to the Madison Campground for three nights, and Fishing Bridge for the other two. If I hadn't called, things could have been a bit messy.
Suggestions...
Don't try to pack in so much driving that you don't enjoy the journey and arrive totally beat... and then have to repeat it on the way back. Perhaps you may want to put Cali off for another day when you either have more time or can fly out for a week or long weekend. Keep in mind that if this your first long trip pulling your rig, you don't yet know your optimal daily routines... how long you're comfortable driving, when you like to stop, etc.
Lots of great places to go and things to see out west. A good way to start is to pick a region, grab an atlas, and pick a few places you think you'd like to go. Examples of regions might be the Southwest (Grand Canyon, Tucson, Sante Fe, etc), the Colorado Rockies (everything from Mesa Verde to Rocky Mountain National Park and all in between), or a northwest loop similar to our this past summer.
If you do choose to do a 'loop', put your longest stretch at the beginning of your trip. For example, we put Grand Tetons NP at the beginning of the trip (four days of driving at our relatively relaxed pace), then worked our way back by way of Yellowstone and the Black Hills in South Dakota. We find that putting the longest distance driving at the beginning of the trip when we're fresh and excited to be on the road works a lot better for us.
And finally, don't over think things. One of the great things about the RV/camping style is the freedom and flexibility you have over finding and reserving hotels, schlepping your bags around, picking a restaurant for meals, etc. etc. etc. Take advantage of it, go with the flow, and feel free to change your plans en route if the desire should strike.
You'll have a GREAT time!
