I am utterly clueless about what would appeal to the LOL generation, but Calibri is probably the "warmest" of the three, and has the benefit of being included with Windows...

I would prefer to go with a san serif font.

They are literate teens, not pre-schoolers.
Don't you think that a serifed type would be more appropriate for print (I presume) articles of this length?
If you're worried about it not looking young or trendy enough, it's not really the job of the text type to convey that quality -- although the way it's set does have some bearing on the matter.

I second Nick's opinion.

If you change your mind and uses a serif, here are some suggestions: Tisa, Dolly, Andulka, Brioni and Karmina. If you go with a sans, Sensibility is a much more interesting option than the three you referred.

Thanks for the help! Good point about serif fonts not dictating the vibe of the magazine. Do you have any system or free serif font suggestions?

Thanks!