Whenever I hear that a friend is heading to Las Vegas, I give them one suggestion.
"Be sure to have drinks on the open-air patio (64th floor up!) at Mix. It is a wonderful (and quiet) way to take in "The Strip" after dinner.
Head to THEhotel at Mandolay Bay and ride the elevator up to MIX lounge. There is a cover charge (typical of Vegas) but for a romantic space where you can enjoy a glass of wine (and this view!) out under the stars, what could be better?