I have three 10 week olds that I've moved outside next to my adult run so they can see each other (I live in NC so it is plenty warm). Anyway, I attempted to introduce them after being next to each other a couple days, and the first thing my alpha hen did was run up to one and peck her in the head!! Of course, I immediately separated them again and I will attempted this again in a week or so. From what I read, it is the size difference in the birds that is going to be the biggest problem. The adults tend to pick on them when they are smaller.
I'm thinking my 10 weekers are going to need a few more weeks of separation. Hopefully, being able to see each other through the wire they will get use to each other while they get bigger.
So, besides that it is too cold where you are right now, I think your little ones are too small to integrate with the adults.
Good luck!