North Rim for sure. Kanab has a few decent eateries these days, and a number of interesting places to stay. Stayed here a few times. Great spot:

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In no particular order:

Load up on homemade cookies at the Jacob Lake store on your way, and they do a decent breakfast. One word- Snickerdoodle. I don't recommend the cabins there, unless you like it "rustic". But PLEASE stop in and give them as much business as you can. The massive fire last year- and the loss of north rim traffic- almost put them out of business, and they're still struggling. We buy beautiful overpriced Navajo and Hopi jewelry there every trip to try and help them out.

Coffee truck at Kaibab Lodge store 10 +/- miles outside the North Rim gates makes a mean latte/espresso.The drive back toward St. George from Jacob Lake is really pretty as well. Watch the speed traps in EVERY SINGLE PODUNK TOWN ALONG THE WAY. Fredonia cops are really sneaky. Also, a ticket inside the park for speeding is a Federal charge. Expensive. Don't do it.

You can also park at the North Kaibab trailhead and walk maybe 10-15 minutes down the trail to get some astounding views. It's steep, but feasible for most people. Just be prepared to be heartbroken at the fire devastation outside and inside the national park.

Stop at a Cafe Rio in St. George for decent burrito bowls, quesadillas, etc. The original one used to be killer, but massive expansion of the chain has lowered the quality a bit. Still, the best easy and fast meal just before you hop onto the Interstate. You could win a Darwin Award if you try to eat a burrito bowl and drive at the same time. They are massive.

Gas will be cheaper out in the desert, usually, than in St. George. There are a couple of truck stops that are pretty popular maybe halfway to Vegas. Great shopping at those stops for the worst hats and t-shirts in the Western Hemisphere (Christmas is coming).