At a minimum +1 with a note at the front desk.

Look were not secret agents here, in fact as we try to be on this site, 'prepared', it makes sense to let the hotel know if your going to be doing something that involves risk and to contact the appropriate business if you don't return on time.

I'm not talking about telling the chick at the front desk of the the Marriott that your family is going to Disneyland for the day and should be back by the 9pm. I'm talking about telling the hotel, ranger station, resort that your going scuba diving, rock climbing, trail running, hiking, etc.