You might also contact the local paper or radio station and say, "My kid has a peanut allergy, and we'd love to participate in a story that reminds your readers/listeners to remember this allergy if they are hoping to create a great Halloween for -every- kid. And to share some strategies for coping if you're like us."
Honestly, that seems a bit snowflakey to me. You can't accomodate every child's allergy. What about the kids who are allergic to dairy, chocolate, eggs, grains or strawberries ? Or the ones who only eat raw, vegan or kosher foods ?
You think it's snowflakey to try to make people aware? Toots wasn't advocating telling people what to do. But there are some of us out there who genuinely do want every child who trick or treats to have a fun night. If there is candy that is appropriate for children with allergies, I would have some on hand, if I knew what it was and where to find it. Most people who hand out Halloween candy do so for the joy of participating in the holiday. Most of us would not be put out by a local radio station or newspaper running a story about where to get candy for children with dietary restrictions. And if you are, ignore the story and hand out whatever you want.
I think people are pretty aware of allergies. I don't know anyone who hasn't heard of them or doesn't know someone who has one. The problem is that there are so many things that are even common allergens. And then you have intolerances, and other things. You can't accommodate everyone. The best each person can do is buy a variety of things and let the Trick-or-Treaters choose if they want sugar, chocolate, organic, etc.
But these are gifts
. Someone's coming to my door asking me for food. And I'm nice enough to spend $25 to buy candy and stand at my door all night handing it out. I have a ton of allergies myself, that's why I buy a variety. But it is special snowflakey to try to announce on the radio or by word of mouth that people should purchase certain kinds of foods to accommodate anyone coming to their door asking for the food.
And when most of the people in North America (I can't speak for the rest of the world) are already aware of allergies, when you mention it for the nine millionth time, it is like beating someone over the head. And looking a gift horse in the mouth. And it sounds a bit like special snowflakes are being condescending and saying that the free candy isn't good enough. It comes across as judging the gift-giver.
If my free dairy-filled, preservative-filled, high chocolate, high sugar gifts that cost me $25 aren't good enough for the people "begging" at my door (I have little kids too, I don't consider them beggars, but that's the word that comes to mind), then I will turn my porch light off and not hand out candy or anything at all. In any economy, but especially this one, there's no way I'm making sure that I give out healthy, allergy free, intolerance free food that costs way more than the $25 I already spent. I can't anticipate every allergy. And I would find it very off-putting to be asked to.