The guests will get the full amount back from Airbnb. You have nothing to do with that, but be curteous and cancel them asap, so they'll know. If you would stay on with Airbnb as a host , you would be penalized for doing the cancellations, that happens through subtractions from your future earnings and having those cancellation dates blocked on your calendar so that you couldn't rent on those dates to someone else. But it sounds like you have to quit hosting through Airbnb all together, so it won't matter to you.
If ever you wanted to come back to Airbnb, they clearly state that it is the host's responsibility to make sure that all legal ramifications are in place and okay, so you won't get much sympathy or leeway from them for the fact that you didn't clearly know or observe your lease agreement. That was/is your responsibility. Sorry 😞