Look at the age of those attending. If many are coffin dodgers (term used pretty frequently on Wake Up With Wogan on Radio 2 apparently) then watch the volume.
I've only ever been asked to crank-up-the-volume a couple of times at a social club event because most of the audience were nearly deaf!
Anyway, I would imagine that the audience will have varying degrees of ages.....so in jest examples, make sure you have Mozart to Moby and Beethoven to Blondie on hand!!!!
Have you got a copy of the National Anthem? What about Relax by FGTH?
Seriously, have a bit of confidence and take along a broad spectrum of music which consists of the popular classics from the 50's to the 90's and you're virtually half-way there.
Never assume that an elderly audience is into one specific genre of music.
Come to think of it, never assume that the audience will have a combined age of 10,000 years either.
There is a possibility that interaction on the mic could work well if those attending happen to be elderly. If you feel at ease, address and talk to guests with ease then you've virtually won everyone over - so try not to clam-up on the mic and equally don't bore with nondescript twaddle either!
And if you have a radio mic then don't hide behind the gear, venture out! Mind, I would take along a spare set of clothing and mouthwash just in case!
If you are married, I would think of an excuse now in case you acquire mature
love gum-bites.
How about a simple approach to the dilemma: Have fun and be your self.