My Husband would make noises. When we were in a store I overheard a child ask her mom "why is that man sad?" (by the way mom quickly tugged the child's hand as if to shush her.)
I said it was ok, and asked the child if they knew anyone in their class that was Autistic. When they said yes I went on to say with Autism the brain does not work like yours or mine. The same with Dementia, his brain does not work as well anymore. I then asked if the child in their class made noises or did other things to comfort themselves. When the child said yes. I told her that was what the noises were that my Husband was making. That he was not sad or hurting. I thanked her for being concerned and assured her that he was fine.
Kids get it, they just want answers they can understand and they want honest answers.

Good article. Recently I had to talk to grandchildren about another grandparent's alzheimer's. I was pretty blunt with what I said. Then I second-guessed myself. But my support group told me I did a good job.