If by "kids" you mean 13 year old boys who like to roleplay battle hardened man killing war heroes who are also only 22 so they can still be considered optimally attractive, with badass skull tattoos who pwn like a million guys with one shot because they're a vampyre prince but they can't get enough blood so that's their weakness it's totally fair...
Then yeah I could see the problem with that. However, I have growing confidence that in many respects, the game will not allow for that. Said plot was easy with, say, World of Warcraft, in which there were an ample amount of wars and fantasy scenarios in which a person could easily craft an unrealistic background. However, in creating a TSW character you more or less have to roll with *real history*, and realistic standards of living. So, it would be quite difficult to be a war hero and also 22 unless you are a veteran of the Iraq war, or you are foreign and have come from civil conflicts within your foreign country, but then by those standards you'd have to incorporate that into your character.
It would also be hard to be super wtf pwn while still keeping up to the standards of the modern day. You can't simply innitiate a blast that would kill al teh z0mbees without destroying modern buildings as collateral damage.
All in all, I'm sure the immature RPers will always find a way to infiltrate, but I have confidence that their immaturity will not be tolerated by the community, and they will be forced to change their character.