I’ve done a bunch of garage sales and I haven’t ever found a reason to be this alarmed. Keeping your cash in your pocket is a good idea, but otherwise, if someone manages to yoink a $2 item, who cares? All I’ve ever had stolen was a VHS tape of Masters of the Universe, and I laughed so hard that it was worth it.
I’ve done a sale mostly solo. You can pick a lull to run inside to use the restroom. No big deal. Help is good, but, not crucial.
I do agree that the date is terrible. I don’t know what’s customary in warmer climes, but garage sales are pretty much over for the season here. As soon as it’s slightly cold, nobody comes out.