Even if they're "cuddle[d] up in the corner" then they're still using electric, still leaving crumbs on the floor, putting dirty feet on furniture, still going

Even if they're "cuddle[d] up in the corner" then they're still using electric, still leaving crumbs on the floor, putting dirty feet on furniture, still going to use the washrooms, etc.. They may seem like little things but they're real costs. I think I'd aim for a tech solution of providing a ticket with purchases over X amount (coffee + danish price) with one hours free log-on. You either then pay for additional web or buy more products or leave.