What dancers and callers understand as “a measure” or “a beat” is not necessarily the same as what professional musicians will understand, depending on how the sheet music was written.
I strongly second the advice of communicating the concept of potatoes and practicing exactly how long you expect the band to play before you start calling, and how to signal the end of tunes. The advantage you do have on that particular front (assuming these are classical musicians) is that they are used to watching a conductor for gestures.
They may have difficulty setting a good starting pace for tunes. I’d tell them to be careful with recordings as those frequently are paced differently and are flourished for listening. One of the finest fiddlers I know once recorded a 9 minute track for me with the preface that it would be great for dancing, but not much to listen to.
I will ask my significant other if she has other advice.