Being a huge fan of afternoon teas, I was quite disappointed with my experience at the Tea Lounge. The only thing saving this review is the service we had and the view.
The afternoon tea was served in what seemed like their lobby. Just a few seats available and a holiday decor separating the room from the concierge. What really surprised me was the price. If you look at their menu online it says that it should be only $40 per person. But during the holidays they offer the nutcracker tea set for a little more and some of the proceeds get donated to the nutcracker show. If you look at the previous price for this it says $45...not bad from the traditional tea price of $40. This year, it is $55! And it was not worth the money. Portions were very small considering what you had paid for. Thankfully they allowed us to share because if you got the afternoon tea by yourself you'd end up paying close to $70 depending how large your party was AND 18% gratuity is automatically included into your bill.
All in all probably would not go back unless the price is a bit cheaper than $55. The only parking option they had is valet and that is $20 per car. So you have to make the walk from aria and pay about $7-12. If you're looking for a bigger portion and cheaper afternoon tea, you can try Petrossian bar at the Bellagio though you won't get the view you do at the Mandarin.