If you have a smart phone, my wife and I use an APP called PDF maps. Its free for both I-phone and Android. Look for national forests along your route by going to this web site:
http://www.fs.fed.us/recreation/programs/ohv/ohv_maps.shtml .
You can search Motor Vehicle Usage Maps (MVUM) for the areas your going through. You can download most for Free with that PDF Maps app. You can also get paper copies of the maps at any of the ranger stations for any given area. Most of the national forest land is free to camp on. If there is a camp site location, the fee is small like $10 a night. Also, I second getting the National Parks year pass. Its like $80 but will pay for itself several times over. It gets you access to all the national parks AND you can get discounts on some state parks and various camp sites. Last Summer we took a 4,500 Mile 2 week trip. Our total cost of camping was around $100 cause we did a lot of national forest camping. We also probably saved somewhere around $300 for park passes and discounts by getting that $80 national park pass. Heck, that thing paid for itself just by going to Yellowstone and the Grand Canyon. The other 10 places we hit were essentially free.
Here's some more advice:
-Find stuff you both want to do. She puts up with your stuff, you put up with her stuff and keep an open mind.
-As someone said. You WILL argue at some point. When the argument is over... its over. whatever you argued about, let it go and move on, and dont bring it up again.
-Don't stress about getting lost. That's the best part and often when you find the coolest stuff.
-Keep an open schedule, Have ideas of what you want to see and do but don't make anything a MUST. The less of a time schedule you have the better things will be.
Finally, remember... If everything goes right. You'll have a story to tell.....If something goes wrong...you'll have a GREAT story to tell.