Introducing 3 month olds to 2 year olds

[doglady60]

I've got 2 Australorps, 1 Buff Orpington, ! Americana and a Bantam Cochin rooster who are all about 2 years old and have been an established flock most of their lives. I have 1 Silkie (don't know boy or girl), Bantam Cochin rooster and Bantam Cochin hen that are now all 3 months old. I've had the younger ones in an exercise pen every day while the older chickens free range for about a month. I've read all the different posts about integrating but I'm concerned because I'm mixing full size and bantam chickens. Right now only my rooster is a bantam. Should I wait longer to try and put them together so that the bantams are bigger? I don't think they will get too much bigger. Any assistance to making the transition easier would be greatly appreciated.