Just print the QR code of one of your public bitcoin (dogecoin or others) addresses so the people at the meeting
can make donations easily using a phone wallet.
I thought it was inappropriate to re-use addresses. Is that not the same for QR codes?
You could generate a new address (and so a new QR code) for each of your presentations or meetings, if you don't want to reuse the address.
Btw, reusing addresses isn't really a big problem. It won't make your bitcoin unsafe, but just make people to be able to link your addresses more easily.