Moab - Hell's Revenge, Poison Spider, or Moab Rim, in that order, if I were to suggest trails for a Razor. Each one will return to the start area. You could leave your tow rig and trailer.

Each one is different and in different parts of town. If you have 2 days for Moab, I'd do Hell's Revenge and Fins and Things while in Sand Flats park. Then you can decide on which other trail. Poison Spider is Awesome without being too much. Moab Rim is pretty aggressive at the beginning. Just remember while on Moab Rim, you are always going Uphill and it's easy to forget about the weight pitching over when side-hilling.
If you are going to see sights in Moab, I'd go to Arches NP and hike to Delicate Arch! NOT the Overlook, Hike TO the Arch. It's about an hour of walking uphill, but it is easily WORTH IT!
Another quick sight in Moab, Dead Horse Point. Quick park to run thru, but Very Beautiful Overlook! WORTH IT TOO!
As for the Grand Canyon, I have been told more than once to go to the North Rim. I did and it is AWESOME! The North Rim is more wooded and like Colorado. Go directly to the Lodge and watch the Sunrise or Sunset, whatever time you get there.
I have not been to the South Rim, but I've heard it is more commercial. Fast Food, Souveniers, Helicopter rides and whatnot.
The North Rim is Quiet, Very Scenic, and very wooded. You can stay in Lake Jacob, AZ. They have some cabins a small cafe and a gas station. From Jacob to the Lodge is all of 50 miles. If you are going to catch a Sunrise plan on leaving at least an hour to hour and a half for time to get there. It will be worth it.
May I suggest a route from Moab to Grand Canyon? I'd take the interstate west, then south thru Bryce Canyon NP and Zion NP. Both very neat parks.
Have Fun! Take Pics!