Why not, I'll chip in half a Bitcoin. Depending on the charity I suppose, there are some really destructive ones out there. Do you have one in mind?
Wow a donator already!
I haven't thought of a charity yet but if you have any ideas let me know, remember I live in the UK so it'll have to be a UK charity.
I could donate to Oxfam since I live near it.
If you're dressing up as a cow, can I recommend Nuzzlets?
http://www.nuzzlets.org.uk/