Sometimes, guests are having so much fun that they forget the specified end time of a dinner or party. Or that, beneath their smiles, the hosts may be really tired and aching for some R&R. What to do? Serving coffee isn't always the best way to cue guests to leave. Especially if it's warm weather, or the client didn't order tea or coffee service. There are other ways to get guests to leave besides the long standing tradition of serving coffee and dessert. Have your catering staff do some or all of the following:
Remove all food, plates, napkins, and the like. You may want to wait to remove the guests actual drink cups/glasses last.
Empty all garbage cans and recycle bins.
Begin moving and/or breaking down tables and chairs. The closer you are to guests when you do this, the more likely they are to get the visual cue to skedaddle.
Break down any bar stations, and remove all beverages.
Hosts, you can also disappear to your bedroom/quarters without saying goodnight. It may seem rude to not say goodbye. But if it's late, I don't think anyone can fault you. I can vouch for the success of this method from trying it at home as a last resort.
Perhaps the best cue of all is for guests to see the catering staff leaving. That happened at a recent event, and the last remaining guests stood up and began saying their goodbyes.