I recommed mounting the alarms high enough to be out of reach. Also, you can put scotch tape over the button to prevent it from "accidentally" being turned off. Another tip - if they seem too loud, put a couple pieces of scotch tape over the square/speaker part and it will muffle the sound a bit. These were lifesavers when my daughter learned how to open a door. I am good about locking the door, but not everyone else it good about it. And eventually she learned how to turn the lock, so these really came in handy!
We use this on our son's door. We have it up high where he can't reach it. the sliding button is very tiny and I'm sure they could mess with it if it were in their reach. I had my husband mount it as high as he could. I stood with my arm up so I could reach it cuz I'm shorter than him, lol. My son doesn't touch it out of fear of hearing the noise go off. If the door is open (connection broken) and you turn it on it will chime or "bong" continually until the door is closed. Once my son heard the loud noises he doesn't go near it, lol, plus it's too high anyway. They're cheap enough to give it a whirl for you, but works like a charm for us! We showed our son, "If you open this door, this is what will happen!" and let it go off.
There is just a switch. The item that looks like a big button on the front is not a button. I believe it is just the speaker. The switch is a standard sliding switch. If children could reach it, they could turn it off, depending on their age and the location of the alarm. On doors, these are usually mounted at the top of the door, well out of reach of children in normal circumstances. The alarms are also pretty small (about 2.5 inches long), so they don't attract much attention.