Best way to integrate chicks into existing flock?

[myfivehens]

We have 6 chicks, five are 6 weeks and one is just a little older (neighbor gave it to us and I didn't ask the age), who are still in the brooder. Out in the coop we have 4 almost 14 week old buff orpingtons, a young D'uccle bantam rooster, and a young bantam frizzle.
I will probably wait until they are at least 8 weeks, if not a little longer. Will they be ok going out with the rest at this age? What are warning signs I should look for that the flock is not accepting them? Thanks!