I agree with previous posters that your best bet to find the things that your lady wants for such a short trip would be the Zona. But if you don't want to do that, why not go down to Playa del Carmen? Smaller, but it has good restaurants and clubs, and Avenida 5ta has become rather chi-chi. For easy access to nightlife you want to stay in town instead of at Playacar.

If you have the bucks, hire a car or get on a collectivo to get there. But it's just as easy to take a comfortable clase premier bus directly from CUN to Playa on ADO, and it's really cheap. Just as convenient to get to Playa from CUN as to get to the Zona, IMHO.

Keep in mind, however, that big indoor clubs, bars, concert venues, theatres etc. are still closed in Mexico by order of the government, in order to limit transmission of H1N1. Outdoor venues, however, are open and no problem. I got back from CUN Saturday, and I wish I could report on Playa for you, but I was vacationing on Isla Mujeres (which is a whole different kind of place).