I see no reason to not make this trip in an X5.

On the return trip, (or while actually spending a few days in Vegas) you have to do the Hoover Dam tour. You will get a sense of the drought in the west while you are there -- the lake is about 200 ft below the normal high tide mark, which is denoted by a white band where the water normally would be. You also need to take the road from the dam to Kingman, and about half way to Kingman there is a left turn that goes to Grand Canyon West, home of Skywalk. Do a Google search on SKYWALK. It's breath taking. You can do the dam tour and Skywalk, and return to Vegas in a day. The dam is about 30 minutes from the strip, and Skywalk is another 1.5 hour drive -- plan on about 2 hours driving one way from the hotel to Skywalk and back, so a total of 4-ish.

In Vegas, skip the strip and go Downtown. Well, don't entirely skip the strip, but also do not miss the downtown area. They have made Fremont Street into a pedestrian mall, and the overhead patio cover is a huge video screen that they play music videos on, and there are speakers up and down the street that the sound comes from. There was a Doors concert the night we were there last. Very cool. You might remember Fremont Street from the 007 movie, Diamonds are Forever. JB was driving a Mustang around the downtown area while the inept cops were chasing him. He put the Mustang on two wheels to drive through a skinny space that the cops crashed trying to keep up. This was filmed on Fremont Street, and the surrounding cross streets.

So, downtown and the strip -- night time is the best time for both of these -- the dam tour, and Skywalk.

I missed your route plan, but Kingman is on I40, and if you turn east from there toward Flagstaff, then when you get to Williams, the South Rim of the Grand Canyon is only about 45 minutes. If you schedule right, you can get sunset and/or sunrise at the South Rim, and this is the best time for pictures. East of Flagstaff, there is a meteor strike that is worth the effort to go see.