Oh yes! - excellent outdoor space just crying out for a folk festival

Landlord sounds happy to put on a barbecue and get in guest ale(s)

Can we have a naming competition or is it Foots Cray Folk Day?

How about -

Foots Cray Folk Week (perhaps too ambitious)
Riverside Folk Festival (probably too many of those already)
Crayside Folk Festival
Sidcup and District Folk Festival
North-West Kent Folk Festival