>>/752714/
I don't see why you couldn't learn a tune they might like. Some pop-bydlo-folk something. You don't have to learn the full song, you tell 'em you learning classical, but you can recall something, you are not sure. Also admit you have stage fright. Ofc they'll laugh at you but who cares.
Plus, you could stall the thing saying you don't want to bring the guitar in (here it's relatively expensive thing, I would care if some gypsy would damage it if I had one). They'll pretend to be very disappointed make some faces, but insist, they'll get over it. After you learnt something to play you could bring in the guitar, like when someone has a bday or something. Or just forget it entirely.