Did some quick Google research. Thankfully this is a hotly debated subject, so there were plenty of helpful results. Unfortunately, it's a hotly debated subject, so there's no clear answers. As far as I understand, this issue comes out with two important factors:
1. Any photography at a public space or private space open to the public is lawful and protected within the United States. So if you're out playing at the park, you're accepting a reasonable risk of being photographed by either a fellow Amtgarder or a passerby. Don't like it? You can ask not to be photographed, but up to the point where the photographer is obviously continuing to photograph you in order to harass/stalk/inflame, they don't necessarily have to comply. Unless you go to the restroom or inside a private residence or build a fort with "keep out" written on it. Then you have a reasonable expectation of privacy. That means basically anything actually Amtgard related at public parks is open to photography. The only time Amtgard happenings are not gonna be open to public scrutiny and photography is when we're at a rented private hall or land, in which case the landlord can make the rules.
2. This is where it gets sticky and is what Collin is asking about, I think. The intent and final disposition of the photographs is where the law gets sticky. If they're just for private use (which should include sharing among friends, even on Facebook, but even there there is some stickiness, which is why Facebook almost always deletes something when someone protests regardless of law and circumstance surrounding the taking of the photograph) then no permission need be sought if the subjects are in a public space. If you take a group photo at Times Square and catch a hundred other people in the background, then share it around as part of your trip album, you're fine and don't need a release from every single person. You should still be fine if you wanted to take that photo and sell fine art prints of it on stretched canvas to New York styled coffee houses (wow that scenario got weirdly specific). It gets stickier if you take a photo of 300 people, most of whom are recognizable in the photograph, and try to use it for an ad campaign. Strictly speaking, you would have to get a release from everyone recognizable in the photograph.
The main difference between the two examples above in number two is the intent to make money off of the photograph. With that in mind, is that what we're attempting to do with our flyers, business cards, etc.? I don't know. I want to say no, as we're a non-profit, tax-exempt organization, but that's more a question for a lawyer, I'm afraid. I don't know if our waivers would exempt us from releases if we fell into the second scenario's sphere of influence... And judging based on what I've found as far as model releases go, the suggested one-line amendment would be insufficient. But again, those releases are for for-profit commercial use, so I don't know if they're the kind of thing we'd have to concern ourselves with.
If this is something that Westmarch really wants to concern ourselves with, we'd have to get in touch and get an opinion from a lawyer, I feel.
Some websites I read doing my quick research:
ByPeople: "Photographers rights, learn everything"American Society of Media Publishers: "Business and Legal FAQAmerican Civil Liberties Union: "Photographers - What To Do If You Are Stopped Or Detained For Taking Photographs"NY Times Lens Blog: "Can You Take a Photograph Anywhere?"Photojojo: "Photography and The Law: Know Your Rights"