Obviously the area needed to put it up is going to be dependent on the size of the booth you’re getting. Doesn’t Abbey Road (whoever they are) give dimensions? I’ve never rented one and don’t have a restaurant, but I do set them up pretty regularly at work. Most of them we do are just a backdrop (think of what celebrities stand in front of at awards shows, etc.), and size depends on what the event is. The dimensions you’ve given are about the same as what we typically use, but again, it depends on the size of the rental equipment. The footprint can increase a lot depending on what kind of structure they’re hanging the drop from.
Silly question…why green screen? Are you planning on having them on video standing in front of something you can’t actually have there? Green screen is used in video production, but not really so much for still pictures. The green paint is chroma key, specially formulated to “disappear” so they can project an image the person/people will appear to be standing in front of, like when the weather folks stand in front of radar maps or whatever on TV.