I like the fact that you don't have two epic rides on the same day anymore. You'll feel all the miles there, as well as the heat (this weeks highs are upper 70s and it's still early April, by mid May it can be pretty warm). I think shorter and/or flexible rides make the perfect second ride of the day, and I'm partial to doing a big ride first, then laying out of the midday heat, eating an early dinner, relaxing, then doing a second ride in the early evening.
Some good short and flexible rides are;
-- The practice loop at the Slickrock trail. It's right at the trailhead and you can combine it with an out and back of the regular Slickrock trail, going as far as you feel like. Might be great for your first day because you may want to try and nab a campspot up the Sand Flats road reasonably early in which case you'll be right there. All the camps up Sand Flats are easy riding distance from the Slickrock TH.
-- Pipe Dream. On the south edge of town. 4.8 miles one way or 8 total round trip. Easiest loop is made by parking at the southern Trailhead, riding the trail back towards town and then either riding the Jeep road (which you will be looking at in the flats the whole ride north) or jumping on hwy 191 and running the asphalt back to your car, or riding the trail back uphill. Fun techy sidehill stuff.
-- Bar M trails. Only 9 miles north of town. Lots of nested loops so you can choose your own adventure and mileage. The jeep roads are strictly for kids and connecting the real trails but the singletracks are great warm down fun. Slickrock may have been the most popular spot in town when nothing else was there except 4wd roads but for my money Circle O has the best slickrock playground that side of Bartletts. You can wander around all you want out there. And North 40, Rockin' A, Deadmans Ridge will keep you entertained for hours.
--My favorite overlooked second ride trail is 7Up. It starts at the Mag 7 Trailhead (park on the highway and ride the first 1.5 miles to the T.H. its all downhill coasting) and is 9.5 miles, but there's enough elevation loss that it feels shorter. The tough thing for you is that you need to shuttle a car (it ends on the same highway, 313, that it starts on) or double your mileage.
Here's a couple other hints nobody has mentioned yet. There's a very nice pool in town, and since school isn't out yet it won't be overrun with kids. Google it up and take a look. Take a suit and a towel, use their showers, and lounge the heat of the afternoon away.
A very nice campground with lots of shade trees and showers is the Pack Creek Campground and RV Park. It costs more than the Sand Flats but shade is your friend and you can reserve in advance so you don't have to worry about all the first come first served spots being full.
Are you planning on jumping on I-70 and blazing east when you leave Moab? If so, here's a sweet alternative. Head SE to Cortez, Co, about two hours from Moab and ride Phil's World instead. Hours of swoopy fun. You will be very happy you did. Then head on east over to Pagosa Springs and find a motel for the night. The can't miss spot in Pagosa is the Overlook Hot Springs. It's in a Victorian Building in town, and has hot springs inside and on the roof (yup). You can't stay there but they are open late and it's only about $10/person. It's really not far out of your way to drive across the more southern route thru CO.
Good luck, have lots of fun.