Are Bitcoin transactions traceable?

I have a question after a silly discussion.

We discussed for the best way for terrorists to get money. I have offered bitcoins. My question is: is it possible to trace who has cashed out bitcoins into money if you know the bitcoin wallet address.

I think it should be possible to trace, but how to trace such a thing?

NOTE: I’m just talking about cashing out bitcoin into money, not buying some cheap stuff.

bitcoin donations tax deductible?

I work as a volunteer for a tax exempt organization in the US. We are currently accepting donations in bitcoin but not issuing receipts for those donations. I would like to start issuing receipts. Is there any legal guidance available online about this? I haven’t been able to find anything.