Byrone, it would be good if you would have stats backing you. You could make a meeting, i am sure your company also has some less lazy workers. So you make a meeting, gather everyone together, and show them stats about the productivity in the office. In that case your not personally insulting anyone.
But i still say you should hire or preferment one of the workers who is responsible, (you dont have to pay him 5x more then others, just a little bit more, not much). But in that case he makes sure things are done. Then you make special meetings with him, discuss what is going on monthly in the office, who is doing what (if you dont have time to check yourself).
Another thing is so called productive paying. Pay for the work. I dont know how you can prove that, but if you can it will be good. In that case your workers get paid for every working hour, if you are already aware of their other actions like Facebook, then on the next pay day, lower their salaries, and if they start shouting, show them those stats. You have the right. (And if you think they have kids at home, what ever, 1-2 months less paid is not a huge problem, they probably also have husbands).
The overall idea is not to punish or create hate in the office, but give out a message. Be productive and you get paid.
In fact if you bring the productive policy in to your company, chances are your company will be more productive, cause every worker wants to show his the best (and eventually wants to get paid most).
The q really is, do all your workers get paid same amount?