That age difference is just a week further apart than I would try it, but that doesn't mean it wouldn't work.  
Right now I have four brooders in my bathroom, one has six week old chicks, one has four? week old chicks, one has chicks almost 2 weeks old, and one has three one-week old ducklings.
I <*ahem*> don't cover my brooders.  I think it's a hoot to watch the chicks practice jumping and perching on the edges.  And then eventually go exploring...  I have some hardware wire separating the 4 wk old chicks and the 6 week old chicks are visiting both of the other chick brooders.  There is no bloodshed because they're "not strangers" now.  But for brooding them all in one brooder, I would definitely have a divider for at least the first few days.  After awhile, you can remove the divider.  This is just so the older chicks don't hog the feeders and waterers.