Yes.
Have you not seen schools decorate local parks as a project? As long as everyone has equal access to the park, the “host” is not profiting off of the park, and he is upfront about the engagement and does not pretend to pay in exposure or anything. This is a fairly common occurrence. In general I’m all for local art studios hosting community art for free, music competitions having the winners composition performed for free, etc. I would hate for those things that benefit artists to be condemned. A lot of important art foundations would no longer be able to operate.