You should. There's nothing wrong with asking for donations especially since it's helping fund an open source project that people use. If anything not asking for donations is worse since there's nothing really supporting the project but your interest in it. By asking for donations your making the project stronger.
I agree. When I was in political activism circles we made CDs and pamphlets and such which we would sell during events. We charged maybe $5 for a CD, a low price, but not zero; we found that if people paid for the material they valued it more, rather than just tossing it aside. I feel this analogy holds some weight in regard to working on open source as well. People don't have to give you much, but if they give something, especially if it's regular, as on Patreon, they'll feel invested into it, and _you_ will feel more serious about it as well. It's a two way signal: that you're investing your time, energy and enthusiasm, and your patrons are thanking you for it.
