Villan, if there's enough interest (and you need to be fairly sure of this first) in having a trad jazz evening at your club, why not go for it. You can publicise it in advance to make sure no disappointed jazz-hating folkies will turn up. It's sometimes fun to have a 'non-folk' evening once in a while (e.g. bluegrass, country or rockabilly, etc.), and the regulars will often enjoy an occasional change from the 'standard' folk stuff. It would be better (IMO) to have a whole themed evening rather than try to combine it with folk - but some may disagree (I'm sure we'll soon find out...)

As for the demise of trad jazz, yes, the Beatles and the 'beat boom' of the early/mid sixties made it suddenly seem 'old hat' with teenagers in particular - the likes of Acker Bilk and Kenny Ball who had enjoyed huge chart success in the late 50s/ early 60s were suddenly nowhere, chart-wise (from about 1964 onwards). But they had the last laugh - they're still going, and where are the Beatles now? :-)