Doesn't sound like you need a card, just an RF remote.
For a dance class, if all you need is music control, any pc rf remote should be fine.
Here are a couple of options....
You should double check these specs but, this is the info I found on the net.
Diamond XtremeTV PVR "Power Pack" editions include the Firefly PC Remote Control. This is a high-end RF remote control that features outstanding design and ease-of-use, and recently was awarded 4 out of 5 stars by PC Magazine.[Link: google.com]
Remotes:[Link: amazon.com][Link: amazon.com]