How did you setup your TS? Is is an application server or administrative?
You'll need to decide which licenses are most beneficial for your situation. I assume you could use either client licenses or device licenses with the setup that you described. I've never bought or installed device licenses, so I'm not 100% sure how they work. Client licenses, OTOH, will let any client connect to a session as long as there is still a license available. IOW, if you have 7 clients XP clients that need to connect to the server, all you would at the most is 7 client access licenses, assuming everyone will be connected at the same time.