Are there requirements for putting in volunteer hours?

Our club is a 501(c)(3) non-profit. And in order to keep our membership rates as low as possible, we require all members to help out wherever they can. This includes spring/fall cleanup days, helping put in and take out docks and jumps, watering newly planted trees, equipment maintenance, costume repair, equipement repair, general clean-up, weed whipping, and many other activities that need to be done to have a great site and a great team.