I say kudos to those girls.
Of the many criticisms I have of Penn State, Thon is not one of them. Well, except for the pediatric cancer narrative. The money goes to the Four Diamonds Foundation, which directs most of it to the medical center endowment. There is some amount that goes directly to families of cancer patients, but not much. The Four Diamonds Form 990 is available online if you're really interested, and the Sarah Ganim did a good article on this for the Harrisburg Patriot.
That said, the kids who collect the funds show amazing dedication and organization, and I applaud their efforts. Give them a few bucks and wish them luck. They don't deserve to be harassed.