How young is your son? Littles and roosters are a bad mix. Children move fast, are noisy, and make roosters nervous. Nervous roosters tend to attack first, ask questions later.
If you coop is close to your bedroom, be prepared for your rooster to crow every time you turn your bedroom light on at night. They also crow during the full moon, if car headlights hit the coop at night, the neighbor's floodlight comes on, or a dog barks.
I wouldn't put a full size rooster in with bantam silkies. Silkies are usually pretty docile, and I could see those two girls getting pretty overmated. You could try going with something like a silkie rooster, but that's still no guarantee of good behavior or quiet. Also, be prepared to explain to your son why chicken mating is so violent looking.
Why are you wanting a rooster?