If you look at the current popup on http://www.domain.com now you can choose between one time and monthly donations with the tabs - but that choice would be more efficient if it was sequential. The psychological background is that people that have committed to donating once have a harder time to say no to upgrading to a monthly donation when they get presented with that choice once they have committed to the one time donation.
So it is about presenting a clear call to action for monthly donations that allow the user to fork the decision: continue with just the coffee or switch to monthly donations.
In this case, Tiny Coffee is the first step and the options in the second tab are for Membership 2 memberships. So ideally start with Tiny Coffee. Click the shopping cart and get redirected to Membership 2 options first with the question: would you consider this instead? And then give the user a choice to continue with the original one time Coffee deal or switch over to monthly Membership.
The 100% perfect solution for this would be if Hustle would allow for A/B testing - then you could determine how much better this approach really works.