young girl's first chickens?

My neighbours girl Anna wants chickens. She is an amazing kid,. She has horses dogs cats and a rabbit. Her dad is building her a coop. She wants a black and a buff silkie. Her mom wants a rooster and they want 4 other standard chickens. I don't know if silkie hens can be in with a standard rooster or not. I received a silver grey dorking from performance that was supposed to be a barnevelder. I think it is a rooster. I heard they were a gentle breed so I am thinking of giving him to her when he is 6 weeks old , along with one of his sister barnies . In this situation would she be better off to have  a silkie rooster.

I know that in my own coop I have never had a problem with the silkie hens (that I used to have) or the Japanese bantam hens (that I have now) with a standard rooster.  he leaves them alone pretty much, other than they are just part of the group he needs to watch over....
maybe there are breeds out there that are more aggressive to the smaller hens, but I know personally I havent had any issue.