This all sounds amazing to me! I'm in Reykjavik when gay pride is on so I'm expecting not to sleep for those few days!
If you go on to the App store there is an Iphone app "appy hour" which is a guide to happy hours in Reykjavik
Do be aware though that beer is expensive (£5+ per pint) so a lot of people buy drinks at the duty free and party at home / in the hotel before going out.