That is a really difficult one. Both my kids have been approached by people claiming to be casting agents, and I always told them it was their decision, but your situation is different, isn't it? I have been so fiercely protective of my son when it comes to the public eye - you will not see my mentioning his name here, and I try to keep my privacy when I post to protect the kids. I feel that public exposure should be their choice, made with a realistic understanding of what is involved, but how do you present the situation you have to a 5 year old?
Just how much exposure would there be? I didn't hestitate to allow my son to be the subject of two graduate thesis papers, and I don't think twice about the filming of a student intern teaching my child's class, but I would never go on a show like Wife Swap or Super Nanny.
I guess the question comes down to what could be gained from it. Do you feel your family would be treated accurately and respectfully, and do you feel that allowing the filming would increase how people understand the spectrum? There is always a cost to being in the public eye, assuming this would put your child there, that we know. But there can also be benefit. Forgetting the fun of being on TV or showing off a great child, neither of which are alone worth the cost IMHO, you have to figure out if there is a real and worthwhile potential benefit. If not, say no.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).