If you're coming in early April, MANY of the passes in the Rockies will have LOTS of snow. Ski season in the Rockies doesn't end until mid to late April, depending on the year's snowfall. Point is, it's likely to be cold in the morning/late afternoon, and weather is somewhat unpredictable.
Las Vegas into Southern Utah, pick up Zion, Bryce Canyon, Capital Reef (could leave that off and head south from Byrce, catching the Mesa Verde/Four Corners area, North Rim of the Grand Canyon, then over to Sante Fe/Taos, north to Pagossa Springs/Durango/Telluride (if it's not snowing). Getting to Bolder that time of year will be really iffy, IMO. More riding in Arizona would fill the void left by the Rockies, though you can see plenty of big mountains without going over the high passes.
The lodges at Zion and Bryce Canyon are really nice places to stay, as is the one at Mesa Verde. Mesa Verde needs a day to see it all. If in Sante Fe, The Governer's Inn is a top rated hotel, withing walking distance of fine dining, all the shopping a person could possibly want, etc. Taos is an eclectic type of place, and would be a natural path back northward/westward. If you do Zion and Bryce, you'll want to have at least a day in each of those locations to fully appreciate all there is to see. Taking full day "rests" between locales could be a way to please the wife, giving her time to shop/sightsee/eat well/do a spa, etc., and still allow both of you to take in as much as is possible. 2-3 hundred mile days in those areas will be a piece of cake.
Vegas is something I guess everyone should see once, depending on what you're into, but I'd much rather spend 2 or 3 days in the Sante Fe area myself, especially if the wife is into artwork, nice Southwestern style jewelry, and great places to eat. Durango Colorado is also a neat town, as is Telluride, but getting over to Telluride may not be doable that time of year. Some of those locations will have to be planned on the fly, depending on the weather.
Do you like to take easy/short walks/hikes? Less than 2 miles? Several nice, easy walks in both of those locations, with beautiful scenery.
The Lodges in the Park system are not 5 star luxury hotels, but are nice "fit into the environment" type of places, with adequate restaurants. They don't turn your bed down and put chocolates on the pillow though. You won't be spending much time in the room at those places anyway, as there is too much to see outside. The Governor's Inn, on the other hand, IS very nice. LOT'S of nice art galleries in Sante Fe, if you and the wife are into that.