How to introduce a Rooster/Hen Combo to my Chickens?

Hi Everyone,
We have 15 Buff Orpington hens who we really love. I didn't want any other type of chicken (although I think some are very adorable) as I really love how peaceful and docile the Buff Orpingtons have turned out to be. I don't have much experience with chickens and if how they are raised has anything to do with it, but my chickens never run or fly away from us as I have seen happen at my friends farmette. Mine actually love to be petted and loved. They will literally walk in front of you and squat down so that you will pick them up. They have become my 21 month old daughter's best friends. For this reason I NEVER wanted a rooster or any other breed.

Well my 13 yr old wanted a rooster and wanted to breed and sell them. I have a friend who has a very docile rooster and assured me you can find a docile rooster. She also has small children and has never had a problem. So I convinced myself to have faith and I put the word out there that I was looking for a docile Buff Orpington rooster. I was contacted by a family who had a rooster for sale. The only problem is that he came with a mate he has been with since birth. I didn't have the heart to separate them and I don't think they would have sold him to me without her. This rooster and hen combo are actually a mix breed of a Buff Orpington hen with an Americauna Rooster. They are about a year old and the hen is laying green eggs. So far the rooster is very docile with my 13 yr old son who had his first "love at first sight" experience with them. My agreement with the family is that the first sign of hostility, I will return the rooster to them. These were their first chickens and they hatched them from fertile eggs given to them. They just really did not want to breed so did not want to keep the rooster, but do not want him to become someone's dinner.

All of this to ask....How do I introduce a rooster who already has a mate? Will it be difficult? I currently have them both in a dog cage in my barn. Should I put the dog cage in the chicken coop? How long will it take for them to get used to each other?

Another thing is that my chickens are free ranged. This family also let their chickens free range. I'm a little iffy about letting them loose right away as they do not know this is "home" yet. How long should I wait until I let them free range?

 

Can someone please help me with this? I still have them in the barn and wondering if I should put them in the coop for the night. How long should I keep them in the cage getting used to each other?