The bird's freindliness depends completely on the bird, but breed also can be a major determining factor. Not all bantams' breeds are known to make good pets. Light breeds such as the Old English Game, Dutch, and Seabright are known to be rather flightily. Heaver bantam breeds such as the Cochin, Braham, and Silkie are known to be friendly and make great pets for all ages.
As for the temperature issue 30 degrees F is pretty mild so I don't think you will have much of a problem. 30 degrees F is a normal day where I live and all of my birds are doing just fine, even my light breeds. If you are still worried that your birds will be cold then heaver bantams would also be a good choice because all of that plumage will help keep them warmer. You can also pick birds with smaller combs/wattles. All in all I think that birds will be fine, you may find that your biggest concerns are supplying non-frozen water and shoveling out the snow so the birds can walk.