IF you manage to trap it, you should dispatch it. In most places it is illegal to "relocate" wildlife. I am assuming you free range? If you free range then you are likely to lose birds to a predator at some point whether it's foxes, coyotes, eagles, hawks, fishers, mink, raccoons, and the list goes on.
 
As others have said, your hens are more likely to kill chicks than adopt them. They are not broody and not in the mothering frame of mind. Chicks would be seen as intruders and likely eliminated. So it's best if you brood and introduce them when they are older. I tend to wait until the newcomers are close in size to the resident hens (in my case 4 months of age). There's no set rule for that age though, it will depend on your hens' personalities.