This will also attract the scammers, who would try and pose as a charity organization, to get in on the Bitcoin action. You have to make 100% sure you are dealing with a verified charity, before you proceed with payment.
You will also have to look out for 3rd party entities, who would claim that they are accepting donations on behalf of these charities. {They would most probably accept it, and charge a fee for their service, if they acctually do pay it to these charities}
We like to help others, but we must make sure that our help are going to the correct people or animals.