I agree, because of the way most of society stigmatizes those in the lifestyle, that if parents swing that they should keep that information at least from their children under the age of 18 or so.
However, we're encountering a big technological problem right now, at least for us boomers. Technology is moving extremely fast. Most adolescents obviously know much more about computers than most of their swinging parents and grandparents do. Otherwise conscientious parents might think that they are doing the best they can to cover their tracks with regard to swinging (obliterating search histories, not posting identifiable pictures, etc.), but unfortunately the kids know a lot more than many of their parents and grandparents do regarding computers.
What might look to us (boomers) as guards against the children finding out are more and more easily unlockable doors to information.
Last year my niece was grounded for a month and had restricted Internet privileges because she tried to access porn sites given to her by her schoolmates. She was 9 years old. The security set up by my (non-swinging) brother and his wife prevented her from seeing them on their home computers, but apparently some of her classmates were able to get access to these sites at their homes other through other avenues.
So, I'm saying, I agree that information about parents swinging should NOT be available to young children, but even with a lot of caution, some parents will be found out. The parents aren't always at fault.
And if we have Internet-savvy kids searching SLS, AFF, and other swinging sites for people in their respective areas -- and whether or not they ID their parents -- what does THAT mean?