My mum is currently sleeping downstairs with her boyfriend while her boyfriend's kids are sleeping in my mum's room. I keep thinking that if I put my arm in the room and turn the light on and off for some time, they will go but I don't know. What should I do?

It not only won't make them go away, it will make your mother and her boyfriend angry with you when the kids wake them up.

are you not in good terms with your mum? is that your home or your mum's home? if not just f**k off!

Why would you want to be so mean to innocent little kids? Really immature

I think so.