Children names are not on the electoral roll. My details are on the electoral roll. If someone was determined to find out information about you and your children, I believe that information is already there on the internet if they are prepared to look hard enough.
The whole point of being penpals is to develop friendships and you can only do that by actually sharing information such as what Barbie doll they like best and cartoons they watch. These are the sort of things my daughter is probably going to be writing about. I've still got some of my penpal letters that I've kept in a scrap book and it is so funny reading the things that had been written at that age.
It would be wonderful if a real friendship develops out of it for my daughter. I had many penpals as I child and I loved it. In fact, I am still friends with two of my penpals.
I do not believe a groomer would go into the trouble to write letters in child's handwriting, use children's vocabulary, draw children pictures, write children stories, decorate the envelopes. Be in the knowledge that the letter will be read out loud to the parents AND be prepared to give me their HOME ADDRESS. That to me seem very unlikely.
What I know of grooming is that it is very secretive, groomers tend to use manipulative and controlling language. Try to normalise sexual content. They ask children not to tell parents of what has been discussed between them. How is that going to happen if my daughter and I will be reading the letters TOGETHER. And after a few weeks/months of writing letters my daughter might say, lets call 'Alice' together. What will the groomer do then?
I appreciate your concern but I just don't think the risk is there.