Mixing older chckens with Pullets

I have five Buff Orpingtons, two Roosters and three hens. From reading blogs about what the ratio should be I decided to get three more hens. I have wanted Light Sussex since I lost my Becky so I went to a breeder and got three pullets. They are much smaller than the Buffs. I was told they were born in April, same as my Buffs, but the size is really not the same. I was wondering if that's because of the breed of did one of the places I got the chickens get mixed up about the date. My main question is how soon can I put them in the same run and coop. I had them separated for about two weeks before I let them out together. The new ones were in the chicken tractor so the Buffs could not hurt them but spend a lot of time looking them over. Currently I let them out together but as you all know the older ones chase the new ones and as long as they don't pounce on and hurt them I let them chase. I want to put all of them in the same coop but am not sure if they will be OK. Is there a method I can try or will they eventually get along. Any advice would be great.Thanks

They will probably do fine in the coop now that they are accustomed to each other outdoors. There will no doubt be some scuffling over roost spots.

Thanks, I let them all together this morning and the poor little ones were chased and pecked at by three of the big ones. I'm still a little nervous since they are so small compared to the others. Maybe I'll keep letting them free range together a little longer and then try the coop at night. Thanks so much for your help...

If you're able, that sounds like a good solution. Just remember that no matter when they go in the coop together, there will still be some scuffles as Judy mentioned. It's all part of establishing the pecking order.

Sounds good. I am going on vacation for a week and I think I will have them spend more time together when I get back. I must be crazy but I hate seeing any of my babies get pecked. Hopefully they will get it sorted out in a timely manner..Thanks so much