Mandalay Bay Hotel/Casino is probably one of the nicer hotels on the Strip, with the exception of Caesars, Bellagio, Venetian. Staying there puts you on the southernmost point on the strip, next to the Luxor. There is a monorail system linking the ManBay and Luxor. There is also a monorail system that runs the entire east side of the strip beginning at the MGM and running north to the Sahara Hotel/Casino.
As far as amenities, check with the hotel about package deals that include spa time. Before moving out here, my wife and I stayed there and were given free day passes to the spa. The HOT, hot, warm, cold tubs is really cool. Eucalyptus steam room with iced towels. Your own locker with fluffy white terry robe and personal grooming stations. Not to mention the massage options, which will cost for sure.
The pool area is by far the best Vegas has. It has a lazy river, wave pool, bars, tube rentals, sand beach. Close by is the Shark Reef, which is basically an underwater tunnel in a huge shark tank. Expensive at $20/head but cool nonetheless.
Great restaurants and bars there. Definitely hit Red Square for some good times and hit Aureole for fine dining, especially if you like wine. You will dig how the lady retrieves the wine bottles.
I recommend taxis for getting around, and I'm sure you'll want to see the sights as well as visit other properties. Walking distances appear short enough, but due to the grand scale of things on the strip, only walk to adjacent properties (ie, don't think about walking from NY NY to Treasure Island.
The Bellagio light/water/music show is best seen at night, showings are q15'. Treasure Island pirate show is gone, replaced by hot chicks in water. Roy was mauled by his hetero-white tiger and is now in LA recovering and rehabilitating Sigfried is unemployed as the Mirage has cancelled their contract. Blue Man Group is a cool show and is next to you at the Luxor, $75/head. The Cirque De Soleil shows are awesome, except the Zumanity show at the NY NY is sexually themed and not as "artistic" as O and Mystere.
Good dining. Excellent dining pretty much anywhere you go. I would recommend Morton's Steakhouse on Paradise and Flamingo, Top of the World restaurant at the top of the Stratosphere, Lawry's for great prime rib, also on Flamingo. All are pricey, but definitely good eats.
Sahara has the most $1 blackjack tables. Hard Rock and Palms is where the beautiful young people kick it. Most casino minimum tables go to $10 after 1700.
Local sites, Hoover Dam of course, Lake Mead, the Strip itself, Red Rock Canyon, Mount Charleston. There are canoe/kayak/tubing adventures from the base of Hoover dam which should be ok as far as temps go in April/May. Rotor and fixed wing tours of the Grand Canyon and in general are pretty expensive, but if you must, knock yourself out!
I believe your wife works as a Nurse at a Trauma Center in Wa, if you want I can show her around the 3rd busiest Level 1 Trauma Center in the USA, probably the world.
hope this helps!