User groups for specific dates within an opportunity

At our organization, we have a core group of construction volunteers who prefer to volunteer on Wednesdays. We just adopted a model where only these consistent Wednesday volunteers and our homebuyers completing required sweat equity may sign up for Wednesdays. In order to make this happen, I had to create a separate opportunity, "Johnson Village - Wednesdays." 

This now means the homebuyers, and volunteers who like to volunteer multiple days/week, have to go to two separate places to sign up for Johnson Village shifts. This has already caused some confusion, mostly with the homebuyers. We would really appreciate if we had the option to adjust particular days for only certain user groups to see, rather than needing to create an entire new opportunity just for them.