WoW runs on just about anything, so if you have 4 PCs/laptops I think you should be able to run 4 clients... with the minimal graphical settings, I don't think it should be a problem. You do need to network them together though, and you'll need to buy a copy of keyclone for each... or use octopus.

The problems would start when trying to switch from one to the other... you can't easily move displays from one laptop to another, so if your main dies, you're pretty much stuck with manually having to go to antoher laptop to control your chars from their (switch leader using a macro, etc).