I did an 80's night recently and didnt have any problems with twits asking for Lady Gaga (I would have played Queen).
The best interpretation is to have an 80's night as it would have been on December 31st 1989. That means you can play 70's too and avoid arguments over 1979 which produced a tonne of good tracks.
Agree with the host the rules up-front. If anyone on the night wants 2010 music refer them to the paying host.
You can always agree to come out of genre in the final hour of the evening, still mixing in the best 80's stuff.
There's enough great 80's music to have a 24 hour marathon set, so I wouldn't worry about running out of material.
Good luck, 80's nights are (IMHO) the best decade nights you can have.