If you actually have a budget for your project, consider making a clear distinction between who is paid a predetermined amount, and who is volunteering without expectation of payment; as far as donations, you could have some documented policy about how donated funds get split between the volunteers based on their roles, and then publicly disclose your donations.

In your reply to @SimpleStacker you also mentioned "in my country"; if your project is significantly tied to a local economy, then the reasonable compensation probably depends on the activity of that local market, even if some of your volunteers are remote workers from somewhere else.