My grandkids play in the same yard my chickens do. I have had several roosters with absolutely no problem from the rooster. Now the GK chasing the birds,,, well,,,
If your rooster is less than 1 YO he needs to grow up. I let cockerel grow up in a bachelor pad. He would be in site of the flock so the others can visit him, but no touching. (I prefer 2YO)
To bring in a new roo, I put them in a bachelor pad where they can see visit but not touch. After a period of time (so I know he is a healthy bird) I swap him in at night (because its easier for me). He can visit through the night with the girls, and get up with them (get them up) in the morning.
Do you have to have a rooster, only if you want chicks. The ladies will still lay, (maybe not as much), and do just fine. One of the ladies may become dominate and take on the job the roo would do. (including mating)