Two weeks is a nice amount of time for a road trip but that time soon fly's by, so you really need to pick an area of interest and spend quality time enjoying it in a relaxed manner. (It is a Honeymoon after all ! ) As suggested, Denver is a good choice and would give you the options to visit the Colorado Rockies combined with Badlands, Yellowstone and some of Utah's great National Parks. A Las Vegas start would allow you to take in the Grand canyon, parts of Colorado and Southern Utah NP's. Alternatively, heading to San Francisco you could do a loop trip to the Grand canyon taking in the National parks of California (Yosemite, Sequoia and Death Valley) and Utah (Capitol Reef, Bryce and Zion) with a visit to Monument Valley and some of the highlights around Page AZ. There is so much to see and do with all options, you really don't need to spend most of your time clocking up extensive miles and only having time to look out through the windshield. There are no bad options, just those that appeal to you the most so do a little research and once you have the basics down we can help with the finer detail.