Any question answered...

Just hire a tiny PA system for the duration of the installation. Maybe just a pair of active monitors would sort you out depending on the size of the installation and the distances at which you need people to hear it, ie people standing close or far away. Inverse square rule I think for wattages.

Google your local disco shops and go chat to them. Like in bike shops they really like talking about their stuff.

I bought a small system form richer sound just now, more money than what I would have liked to paid but at least it sorted, renting is likely to cost near as much as the show needs to be up for 3 weeks... Suppose now I could rent mine out next year to get some money back... Or sell it or whatever....