The ruling on Music and Fundraising using Ḥarām Means

We are an Islamic School and wish to raise funds to construct a toilet block. We have been advised to hold a musical show. We are told that Mufti Kifayatullah has given a legal edict that permits the usage of riba [usury] for the construction of toilets. Would the same reasoning apply here as well? Also, should we be incorrect in our initial assumption, what if there were no other means to raise funds? Will this be deemed a case of darurah [necessity] and thereby render it permissible?