The two-week olds are still a bit too young to try merging with the older chicks. You need to be patient a week or two longer.
Keep the chicks side by side as you have been doing so the babies can observe and learn the temperaments of the older chicks.
It won't be easy integrating these two groups because the older ones vastly outnumber the babies. You've indicated the babies are black. are there any similar colored ones in the older group? That could pose a problem if these two are so obviously different. Just be aware that it's one reason for chicks to be bullied. There are ways around the problem by introducing similar appearing "stuff" into their midst so the focus is spread around to something other than just two black chicks.
In a week, you can try letting one of the most docile of the older chicks in with the babies to see how they interact. If it goes well, you can add another of the least aggressive of the older chicks. Keep doing that until you're down to the most aggressive ones, and by that time, the small ones have formed a bond with the older docile chicks, hopefully, constituting an alliance.
Theoretically. You won't know until you try it. But two-week old chicks are still too young. They need one more week.
By all means transfer the entire group to the coop where they will have more room. It will go much better when you start integrating the two groups. Have you given any thought to heating the new babies with the heating pad system? It will make it so much easier moving them to the coop since the older chicks won't need heat, but the babies will for another two weeks at least.