@ColeVanD, I think that you should charge both members and nonmembers. I would recommend $5 for members and $40 for non-members. This is something that I would encourage for all workshops.
The token charge to members signals that your time is important and valuable, and will weed out anyone that is not serious about learning the skills that you are teaching. People do sign up for workshops just because they are free, and this doesn’t always add to the success of the workshop.
If you decided to do this, you could pocket the $5/head, you could use it to get some materials/refreshments for the workshop, or you could donate it to the space. Or anything else, including a combination of the above.
$40 for non-members has been pretty standard for a 1-3 hour workshop with low material costs.