I'm curious who told you it had to be "local". None of the organizations I've designated my UW contribution to have been local. (And to those places' credit, UW only gives them my name, so the first time around, somebody at each charity actually looked me up to mail me their thank yous, even when it wasn't a large amount). And this was on both the old paper pledge and the electronic pledge.
If you do everything through the electronic pledge form, you can do practically anything, and no supervisor is going to scrutinize it and say "I don't think you can do ________" because the web site does all the checking.
I do my pledge early so that when they do come around I can just hand the printout over and go "see ya".
Some local UWs try to discourage the specific donation because they want to have more discretionary funds. But they can't demand. Of course, local management can interpret that improperly.
Hopefully if you haven't given try to put your choice on the list, if you haven't filled out a paper pledge, go online and do it, no one will question your choices then!