How many new birds, and how many existing birds?
When I've added groups of birds, I just add them in. I've done this multiple times and had good results. Adding groups is different than adding one or two new birds, it's a different dynamic. There's still a lot for them to sort out, but it prevents the entire established flock from ganging up on one or two new birds and making things too hard on them. Having several newcomers to deal with is kind of like a rooster having enough hens to mate----the established birds spread the dominance over the entire group of newcomers, instead of focusing on one particular bird.
I think what I'd do is let your flock out, and put the new birds in the kennel. You'll want to leave the new birds in the kennel for a few days anyway to imprint on them where home is. So, old birds out, new birds in. I'd do that for the day, keeping them separate. Then in the evening, let the old birds back in. Maybe make them wait until a bit after dusk, so the new birds have already gone to bed and the old birds are more eager to get on the roost, not so interested in squabbling with the newbies. Just see how things go in the morning when everyone wakes up. If you have plenty of space, they should be fine. I'd set up some hiding places inside the kennel for the newbies to hide behind, breaking line of sight can do wonders. Maybe double up on feeders and waterers, although I've not really had birds persistently chase others away from those.
