Torchwood.TV has a post taken from the new Torchwood Magazine about forthcoming audio dramas, which reveals Children Of Earth transmission details.
The episodes... will air as part of Radio 4s Afternoon Play slot from 2:15pm (it's likely they'll air all in the same week, in June). Its stated that they're set... before Children of Earth - which airs a week or so after the radio series concludes.
So its June or early July for Torchwood Children of Earth! It keeps moving up, but with no Doctor Who for six months, having this in the break is good!