I'd suspect that "Steel Drivin' Man" should be good for a chuckle or two to lighten the mood.

The CW "If I Said You Have a Beautiful Body Would You Hold It Against Me" likely wouldn't go over well with actual "naturists" as they tend to be rather "conservative" (in the non-political sense) with respect to sexual suggestiveness; but for a "pretend naughty" group sing (like some skinny-dippings) it might be okay.

"(Gimme That) Old Time Religion" sometimes includes:

Let me worship like the Dru-ids
Drinking stange exotic flu-ids
Runnin' naked through the wo-ids
It's good enough for me.

A question that arises is that if there are to be instrumentalists participating will there being anyone bold enough to play a squeeze box? (Even at arms length? - or maybe we should say "chest high"?)

John