I like all hotels from MGM property (MGM Grand and Mandalay Bay e.g. are very good IMO) but I think the rooms in the new city center are very nice because they are brand new. Which hotel you ever choose keep an eye on http://www.vegas-hotels-online.com - you will find there the latest hotel promotion codes for these hotels, also for Aria and Vdara which are located in the new city center.
City Center would be the best right now but it is expensive. Your best bet would be the MGM Grand. They have been running some good promotions.The center of the strip is pretty much owned by Harrahs with Bellagio and Mirage as their only remaining center strip properties.
Go for the hotels in the CityCenter, as they are having specials since they opened last week.For The Signature at the MGM Grand, try to use promo code SIG986 for a Junior Suite at $119.00 that included a $100 credit for dining at any Aria restaurant as well as a $50 cocktail credit at any MGM Grand bar.
I think Mirage would be a good resort for them. It s not overwhelmingly large like MGM, and it has a nice atmosphere. It s also located in the center of the strip, near many attractions, other casinos, and good shopping.
I would say City Center....Vdara specifically. Its non-smoking and non-gaming. However; there is a walk way to Aria which is a 5 minute walk and has a full casino. There is a ton of shopping there and restaurants. AND its brand new, the rooms are amazing and view is awesome!
The MGM is huge and can be a hassle to travel through the casino to get to rooms. If your parents are older may be a problem. The Mirage is nice is more centered in the middle of the strip.
MGM Mirage corporation has multiple properties. Since they won t spend that much time in the room get the best deal like at Excalibur. Check out www.lasvegasnow.com which is TV8 web with links and info
City Center is a dump. Go to Circus Circus.