Our first dog was a black lab. Way before my husband and I had the 3 boys. Sam was a wonderful dog who just never took to kids under the age of 8 give or take a few years. He never bit, he'd just turn his back to them and give him his rear to pet. It was just the way he was. It never changed.
Thankfully Renie doesn't share that problem. He loves kids, but not being hugged. That in mind I have no problem not allowing strange children to pet him. I was training him on walking without pulling this weekend. A small child wanted to approach and we were just starting our walk. He was very excited and not in the right frame of mind. I knew he wouldn't bite, but I was worried he'd jump up and the child was small. (Ren is only a year old, so we're still working on those things.) I smiled and said, "I'm sorry we're training right now." And I kept on walking. It was a tip I read a while ago and I use it when I'm not certain of a situation. It works beautifully and you are being polite. I believe 100% with protecting your dog. If we were at the end of the walk then I would have put him in a sit and allowed it.The child was calm. Renie just wasn't yet at that point. He was excited to walk.
I didn't know there was a sandcastle kennels, pretty name. I use that name because the year the internet went in our house, we had just returned from vacation. So I chose the name sandcastle. 97 is the year my first son was born. Since he was our only child way back then I chose his year of both because sandcastle is a common word.