Spending a day at the beach/pool and in this weather, a cabana is worth it! Today's price for cabanas are $425. The cabanas by the lazy river starts at $700. A nice tv, ceiling fan (just blows hot air), endless supply of water bottles and towels, tubes, and the waiter/waitress will take rounds to each cabana and take orders on food and drinks (can pay or charge to your room). I would say it's a great deal and make the most of your stay here!
Ps: Make sure to bring your ID because they will check even if you aren't getting alcoholic beverages AND your ROOM CARD (only Mandalay Bay guests may stay here)