Wedding Band Audio

Hello everyone, I have a question about methods for getting decent audio from a reception with a band. I prefer working with DJs because then I can edit the dancing to an aiff file of the appropriate song, but lately I am getting more and more brides with bands and my shotgun mic just doesn't sound that great. Everytime I turn away from the speakers or get in the middle of the crowded dance floor the band audio becomes muted and muffled. What do you guys do to get great audio from a band? I have heard that there is a usb device that could be plugged into their mixer to record and then synched up in post, anyone gone this route? If not, what do you do?

Thanks!