It might not be so much a reservation that's required as a permit, even if there aren't neighbors; many municipalities have restrictions both on use of public parks after dark and on amplified music. The last thing you want is to have your party broken up by the cops. There's probably a parks department or something like that that can tell you.

Also, I suggest using skip-change, rather than pas de basque, to test uneven or slippery surfaces like lawns, since it's affected more by those things.

And I also heartily approve.