How about holding an old-fashioned potluck? Or you could try setting up a picnic at the beach or park . . . it might be less likely to be canceled if food is involved.
I don´t really have friends anymore, but before she moved away, my best friend was just as frugal as I was, so we would hit parks and alternate houses and once in a while, we´d take the kids out and get a cheap special at the local chicken fast food place, while the kids ate chunks of fruit that we brought along!