I would say "Could you please sanitise your hands before proceeding?"

Hi, Grammatically the sentence would be: Let me sanitize your hand with alcohol. (Not let's). But it implies that you are the one rubbing the alcohol on the person's hand, which wouldn't be very sanitary. Even young children can do it themselves. I've heard sentences like this: Please use hand sanitizer. Please use hand sanitizer before entering this office. Please disinfect your hands with sanitizer. Please allow me to make a few simple corrections to your other sentences. "... I have to make every visitor to sanitize their hands..." (Incorrect) I have to make every visitor sanitize their hands... (correct) "Could you guys tell me how should I say ...." (incorrect) Could you guys tell me how I should say...: (correct) Would you please tell me how I should say... (much bettter, in my opinion)

Please use THE hand sanitizer.

If you should be the one who rubs customers' hands with alcohol, you would tell each and every customer "Let me sanitize your hands with alcohol". I guess you didn't mean such excessive hospitality, though.

Would you like to sanitize your hand?