I don't think this is a very good argument. A UPS driver/truck is temporary, and isn't a part of your business. That's like saying you have to put up a Prop 65 disclaimer for your place of business because someones shoes might have a cancer causing chemical in it.

If your place of business is actively adding cameras, and is actively using facial recognition, those are actions that your business has taken. A temporary action of another party should require you to do a disclaimer. Especially if the same action is something they should be disclaiming.