Since no one has answered so far, I'll try the best I can.  I've never introduced chicks that young to an adult hen without a mama hen around, or a wire cage.  
I think since the hen is so much bigger than the chicks, the best thing would be to get some deer netting, hardware cloth, whatever, and put up a barrier between them for a couple days so they can fully see each other but the hen can't chase & peck.  Unless she's a foul-tempered hen, she should get along with them after a bit, with some initial pecking.  What breed is your hen and what breeds are the chicks? Can they run fast or fly, or are they Silkies, or what?