(1) Facebook Event
Draw a geofence(s) around the location of the 'social gathering' and set the geofence to 'on exit'. As a person leaves the geofence you can send a campaign to them with a link to your next Facebook event.
(2) Instagram Competition
Draw a geofence(s) outside your store and set it to 'on entry'. As the user enters the geofence automatically send a campaign that asks them to Instagram an image of the storefront or shop window and tweet it to '@twitterhandle' '#NameOfCompetition'