Photoshop composite.
Shoot a photo of the people, positioned on chairs, tables, or whatever to get them up in the air. Remove the people and whatever was holding them up and shoot a photo of the background without them. Do both photos on a tripod and use the same settings for ISO, aperture, shutter and focus (lock them in when you set up the first shot).
Bring the two photos together as separate layers in photoshop, with the people picture on the top layer. Use a mask and a soft paintbrush to paint away the chair or table or whatever was holding the people up, revealing instead the background in the layer beneath. Get the paintbrush crisp when you get around the people.
Clone and heal if necessary to do any cleanup.
Alternately, cut out the people from the people photo, and paste them into the background, positioned wherever you like. If you do this, pay attention to the light on them, so that it matches the light in the background. Use feathering to keep it from looking too fake.