I would definitely ask the owner.

As a general guideline, cruise lines charge $12-$20 per person, per day for gratuities. Marc and I recently paid $640 in gratuities on a 16 day transatlantic cruise. It was well worth it for the service we received, and we tipped another $100 or so to bartenders, waitstaff and our cabin attendant.
And, of course, there were many people who were in the customer service line, asking to remove or adjust their gratuities.

It’s all what you’re comfortable with.