"Wang chung", in Chinese, translates to "yellow bell", which is structurally adjective-noun.

"Everybody wang chung, tonight", then, diagrams as personal noun-adjective-noun-noun, which is not a sentence, nor does "everybody yellow bell, tonight" make any sense...

"Wang Chung" is also the band's name, so it could be taken as a personal noun instead of adjective-noun, but then the sentence diagrams out to personal noun-personal noun-noun... and that doesn't work either, and makes even less contextual sense.

So, it must be concluded that the sentence has to follow the previous sentence pattern of personal noun-verb-noun-noun ("everybody have fun, tonight"), meaning "wang" in this context is a verb.

Thus, 'wanging chung' is the correct active tense, and not 'wang chunging' or even less correct, 'chunging wang'.

Thank you.