I think this topic can be blown way out of proportion. My suggestion is that you have people pose for photos and don't just post candid shots. Have a policy that you tape to the door to the event and post to fb or other site that says you will take down any photo no questions asked. If someone asks you to take down all of them just do so. Just don't fight anything, make sure people are aware that a camera is taking a picture of them, and make sure it's all in fun. Not one celebrity is asked permission to get their picture taken. You can be really cautious about this as any attorney would recommend and you can have people sign waivers, etc., but then it won't be real and fun. Either have fun with it or just don't do it at all.
Specific notes to your questions:
- I don't see why minors should not be allowed, but make sure a parent or guardian is aware and they are posing for the photo. If you're nervous about it then just don't do it, but verbal consent should be fine in my opinion.
- I don't see how this has anything to do with fair housing. You probably have fair housing logos on all your other marketing materials, and you can put a fair housing statement on your facebook page. People get way too nervous about this in my opinion.
- Probably depends on what you're using the photos for. If you are putting them in an advertisement, yes. If you're just posting them to facebook then I don't see why it's necessary as long as you get a verbal yes from someone. Again, any attorney will tell you to go to the Nth degree to CYA, but the odds of someone saying something are minor and you can always delete them.
I'm much more open about all of this I suppose, and some larger companies haven't even ventured into the social media waters because of their legal concerns. I just say that if you are going to do it just go for it. You don't have to overdo anything, but some nice photos of people posing around the pool at the summer pool party just shouldn't be an issue. I know $h1+ happens, but there are plenty of crazier things out there going on that could get you in trouble. Some casual pictures should be the least of your concerns.