I'd scout out metered parking v. paid parking lots/garages, etc. and just let everyone know, as an FYI. I know if I don't carry change, so if I ended up having to park on the street, at a meter, and all it took were coins, I'd be SOL! But letting everyone know allows them to make sure they have change, arrange to carpool etc.
And you're not really "providing" parking; you're hosting, and I'd like to think as its in a downtown area, most people will figure out they might have to pay to park.