I got your idea! Seems good. But hard-code the list on the source-code.
Just wanted to answer this:
Your idea of governments receiving the donation, sounds more like a government tax, and in a world of so many different governments, some of them abusing the people rights, it sounds a bad idea to me. Maybe work if the idea is to create a "national" crypto-currency managed directly by the country.
As I stated, people select which country to pay taxes to. So, If someone wants to send their money to a corrupt country, what should we say about that? If you live in a given honest country, you would certainly select it as a receiver of the taxes.
Anyway, charity seems a pretty good aim, and there should be no problem in adding countries there alongside with charity institutions, so that anyone can chose where to send money.
Moreover, instead of just giving all the 2% to one entity, anyone could select how to distribute contributions over a set of addresses.
Imagine (relative to the 2%):
80% -> charity
15% -> Portugal
5% -> France
After writing this up, I approve your idea even strongly! And if you "sell" your idea alongside with the possibility to pay taxes, I think It has a strong possibility to be accepted by countries,where bitcoin does not.