Lots of folks on this forum keep their bantams and standards together. I am not one of them, however.
I only keep bantams now, but when I had standard birds they were kept in their own coop and run. When I'd let the big birds out to free range, they'd constantly hop the bantam fence and terrorize my poor little birds (which eventually led to me getting rid of them).
If you're brooding them all together as chicks, I don't see much of a problem. If you're integrating two flocks, supervise very carefully. It certainly can be done, but in my opinion, it really depends on how mellow the birds are and how you go about combining them. Good luck!