Dancing with the Stars=Owned By Disney/ABC Domestic Television
Toxic= owned by two companies, Sony/ATV music publishing LLC, BMG Rights Management US LLC
The copyright law is, you must obtain the legal permissions of three parties listed above to use the work. DADT, SATVMPLLC, and BMGRMUSLLC, if you do not the three parties reserve the right to sue you for a lot of money.
if you use the dancing with the stars image on the shirt, Disney/ABC domestic television will issue you a cease and desist order advising the entire order be destroyed, and to comply with all other requests they may issue.
if you do not comply with it, one of them or both of them will take you to court, they have a very powerful legal team, and you will be sued to kingdom come/out of house and home. the company to sue you first will not be ABC, ABC will not carry a lawsuit out. its owners will carry a lawsuit out on you, The Walt Disney Company and Disney Enterprises Incorporated.
the lawyers they have are very powerful, you have no chance at winning, they very aggressively protect Intellectual property, you will be gone after until they get what they want from you, charity or not.
Toxic's writers, you will be issued a cease and desist by Britney's legal team, you do not comply with that, it goes through Sony and the BMG group. Britney at the time was signed to Jive Records, Jive no longer exists as that was absorbed into the Sony BMG system. and its now defunct.
Sony/ATV music publishing and BMG Rights Management US LLC will sue you for damage for the slightest use of Toxic, you'll be out of house and home, and their lawyers will win against you charity or not.
you will need to obtain the clearances to use the work, no clearances, you don't do the venture, simple as that.