Ask the couple what they want to do for a first dance! If they havn't a clue, suggest the band plays a waltz and they have a smooch - invite the guests to take photos "first dance together as man and wife (or 'as a formal couple' if gay)" - after two or three times through the tune, invite the rest of the gueasts to joine them on the floor "it gets very lonely up there on your own". DO NOT get experienced dancers to demonstrate steps - its a wedding ceilidh not a dance class: people are there ONLY to enjoy themselves and themselves. Make sure you call Haste to the Wedding - it's a good introduction and a good mixer.