Get the entire body, head to toe, on tape. If the couple is too close to the camera, this may not be possible, do whatever you think is best. As a couple comes towards the camera, lead them by hitting the wide-angle button. Likewise as they move away, slowly zoom after them to always keep the camera as tight as possible. Pan slowly and smoothly.
Quick jumps are annoying and difficult to watch later.
It is better to not have a couple on screen for a few seconds than to quickly pan to get someone on screen. The same is true for zooming, try to do so slowly. To switch between couples, watch one, and when they move away, or when a second comes into view, move over to the new couple. This is much better than jumping across the floor. You can concentrate your vision on one eye or the other to see the respecitive view.