We will leave this one up to you. But generally, our insight would be that the stewards set a price that they anticipate will cover the entire cost of your participation in the activity. However, we understand that we set a very high standard for our stewards and expect their guidance to blow you away in hospitality and guest experience. So if you want to show your appreciation, feel free!
Additionally, if you enjoy your activity and want to let your steward know; write a review of your experience and encourage other users to book. We are more about building and expanding community than anything else!