My suggestion:
A dharma teacher provides value. Here in the west (and in my humble version of how this relationship should work) the teacher receives, in return for their value, something of value from those who have received the teaching -- money. It's pretty simple and straightforward and, well, honest... and familiar to westerners. I don't see how a pure dona model would work well here, especially in the case of someone like you, Kenneth, sans a monastery and an infrastructure that model presupposes. And who the heck wants to become a street beggar, for goodness sake?
So my advice is to stick to an open, honest, prearranged relationship based on an exchange of value with your students. This tells them what to expect of you and in turn presents them with a model they know well and can relate to more easily. Also, I've been working with you under your current operating principle, in which I pay for your time based on what my time is worth in my work. I think that's very, very fair and sets a reasonable expectation that, once again, fosters an honest exchange. It also gets you paid, which is of no small importance.
Simply put, drop the Buddhist tradition that made sense a thousand years ago, in Asia. I think it's ridiculous to pretend that a dharma teacher is materially different than any other professional teacher-type person. If you become famous and hire a publicist I will never hold that against you as long as you continue to proivide me with value. I might even consider that a sign of your wild success and expect to pay more for your extraordinarily valuable time