You have to remember to cancel at the end of three years or else it auto renews (triennially) for $251.64. Hopefully I will still be using Google Calendar then and get the reminder
Try the "fun" saturday first, if you don't see any interest then offer to give the day off. If you give the day off first and then ask people to come in, you might not get a positive response.
Also, why does it have to Saturdays? Employees with children might like a day off during the week, to do things which are harder to accomplish in the weekend.
I went to primary school in Mumbai where we had Thursdays and Saturdays off. I liked the break in the middle of the week, but I'm not sure if my sentiments were universally shared.