How to prevent visitors from touching your system

When I got my first JBLs, Dorian S12 we had a cat. He liked the grills a bit too much. Being the 60s and in Chicago there were tons of plastic furniture cover makers. Had 2 flat bottom bags made of clear vinyl. Put over the speakers. Worked like a champ. Cat tried a few times but all he did was slide so he gave up.

Life is too short.  Let them touch, supervised, and clean it later. After the first time they handle it they will have their curiosity satisfied, especially if it’s little kids. 

As long as they don’t mess with the tonearm I really don’t care or see what harm they could do.  (I’m assuming they won’t be reaching around back and messing with cables😂).

All my friends know me and my audio equipment, they know if they touch I keep that hand, so far in 45+ years of audio ownership I haven't had to put any hands into my collectibles.

They need to learn respect for other people and their belongings. I have a seven year old nephew and he understands not to touch it. I explained what all the equipment does and also how a turntable works. Although before I could explain records, he grabbed a brand new one with his whole hand. One side now had a nice thumb print, the other had four fingerprints. He thought of it as a large CD/DVD, I was mad, but once I explained how to handle records and it's been no problem. Besides, it was a just a record, my nephew is more important.

So, if a seven year old understands it, I would hope your adult friends can understand it. If not, use it as a teaching lesson - what it all does and how to use it.