You have a beautiful apartment and great reviews. Congratulations!
I would suggest a lock on the guests bedroom door. Guests don't know you any more than you know them. You wouldn't rent an apartment without a lock because most apartments have locks. If you look at your competitors and they have a bedroom that locks and you don't, guests are going to choose the usual and makes them feel security.
It's been a while since you posted and you've got some support from @Marie8425 and @Shelley159 here. I wondered if you had an opportunity to read their replies?