Kids are wonderful, arent' they - forever making you spin your gears.
I have 4 - been there, done that!
When I was a child I developed different strange phobias of various things like plumbing pipes and so on - walk by some exposed gas meter lines or plumbing fixtures in a parking lot and I'd shake with fear. This actually suck with me for years. I got over most things just with time but it wasn't until I had to start doing work on my own house that I completely got over issues. Once I learned what things were - what they did - why they looked that way - I was fine.
But that wasn't easy - my husband was deployed and my toilet wouldn't stop running. I let it go for 2 months before I asked my Mom to help me fix it - like a total idiot - she was there with me when I sopped water out of the tank. I was actually petrified but she was proud that I finally got past it.
Obviously I'm over all that seeing as how I've replaced all the plumbing fixtures in the house - including having done work on the septic pipes that collapsed last year.
So with my kids I always explain things - everything - to my kids so they fully understand what things are and why it looks that way. It satisfies curiosity and settles any nerves and I always answer questions and sometimes have them help me with this and that so there are no mysteries in life or the walls.