If it were me, I'd provide information about luggage storage options - or if there aren't any options, charge a separate fee for it. But I'd say a firm NO to an 8am drop off. I'd suggest that you say the earliest luggage drop-off time is around your check-out time, and also be clear that "dropping off" luggage is exactly only just that. No quick bathroom use or freshening up allowed. You meet the guest at the door, take the bags, say "see you later at 5pm" and shut the door.
Recently my guest told me she'll be "dropping off her luggage right around check-in time". She arrived, we greeted each other. She went into the guest room, put her luggage down, came out, told me "I'll be back after dinner. Thanks!" and left. This is what "dropping off luggage" means.