The characters ought to not be too experienced, probably with a few Pokemon with levels ranging from 5-11, somewhere in that area? Of course, starting out with obtaining your first Pokemon from the lab would also be acceptable, it'd be a valid reason for taking the tour, too. 

Though the technology exists to see Shadow Aura, I would be fine with having a character that could see it naturally like Rui did in Colosseum. Could be pretty interesting, I say go for it if you wanna! I've never touched the subject of being able to see Shadow Aura like that, so it'd be interesting to see someone else's thoughts and explanation of it in an RP.