The time involved can eat into a day - at least when arriving and everyone wants to go ashore. The ship will move those on it's tours ashore as a priority, which means those booking their own excursions may have to wait a bit. I wouldn't book anything that started less than an hour and a half after the ship arrives - in other words if you arrive at 8am, the earliest tour I'd book would be for 9:30am. Tender ports usually find us booking any tours through the ship since this means we won't have to worry.
However, most tour operators know the drill and have a good sense for how long it will take to tender. They'll let you know if booking a certain tour at a certain time will work or not.