Well, if you want to select 3 unique users on a server with 2 people only, you'll have a problem.
So, firstly try to get some more testers online, I think 4 or 5 will be enough.
I suppose you just pick a random PLID from an array? If so, you should make a do ... until loop and check every nickname if it's not listed in the array from 'choosen draggers'.
It would help us to find a solution if you posted some bit of code here.