I may be reading this wrong. But it sounds like you are over complicating. Surely if you just make a script which sends 2 different print layouts to 2 different printers, the operating system will handle the rest? If all the machines and 2 printers are on the same network, don't the print queues on the individual macs, just wait for there turn on the printer? Am I missing something?
As far as I know, if your script uses print setup to refer by name to "Printer A" and you run the script on another computer where the same driver is installed with the same name, it will work, but I suggest running some tests with your system to be sure.
You may want to investigate a plug in called MyFMButler as it offers a number of options for setting up much more detailed control of via scripts of the printing process.
Phil - I think your suggestion for the MyFMButler may be the best. Looking through the documentation I would have the ability to test for and handle the cases where the appropriate printer is not present gracefully.
Daniel - 2 things. First the label printers are not networked, we just have several or the exact same model. (The one FedEx gives you for free if you ship enough stuff with them. They are not networkable) Second even with a networked printer the queue could be named differently on different computers. If the printer is named wrong on a system that tries to print to it something bad is going to happen. I'm going to have to do some kind of testing to see what that is or how bad it is. Either way I don't think you can come up with a way to test for this before and handle the exception so I think I have to look to the plug in Phil recommended.