Especially with all of the holidays coming up, there will be a lot of big swingers' and sex-positive/bdsm club parties. Those are what immediately come to mind if you're looking for a bunch of people who are open to meeting, flirting, dancing, and even more, in a safe, sexually-charged environment. There's certainly no rule or expectation of people doing more than they're comfortable with at good sex-positive events. So, if you and your wife decide you just want to go and take it all in visually, that's great. If you two decide additional steps (flirting, dancing, certain types of contact) are OK, great. You should obviously discuss everything you can think of and set up agreements about what is and is not OK for each of you in advance AND have a solid plan in case someone becomes uncomfortable during. Then stick to those agreements; you can always attend another event and expand your horizons if it feels right to do so in the future.
Anyway, that's where I'd take this. I would not count on finding people I'm attracted to at any event, just that I'd go and have a good time seeing the sights/doing something different with my spouse. Sex-positive folks are just regular people, so there will be events with lots of people a given guest has ZERO interest in, and some events where there's more chemistry among the guests. Unless a person decides it's really NOT their cup of tea, it's a good idea to keep checking out different groups and events to see if which might be the best fit. IME, most of the people in the sex-positive community who attend groups/events are 35+ (and the majority are in their 40s and 50s), so if you're seeking a younger crowd, you'll want to look for that type of group or party ahead of time. You can always ask group or party organizers where most of their guests typically are on the age spectrum - they should have an idea of what their main demographic is and be open to answering questions from newcomers.
You can google for groups, clubs and parties, but SwingersBoard is a great forum and you can find out about swingers parties on SwingLifeStyle (SLS Personals) as well. If you join SLS, you'll probably get invites to local parties from organizers in your area (they may or may not be good parties--putting them on is a business--so do your due diligence prior to getting your hopes up and forking over the entrance fee!). Most major cities have at least one sex-positive or BDSM club as well as swingers' clubs, and those typically have large special parties for holidays and such as well.
Mmm...sex and chocolate!
I'd love to hear what you think of my story, Truffles with a Tryst!