User blog comment:Rassilon of Old/Young Justice spoilers at Comic-Con 2012/@comment-188.60.137.84-20120813161715/@comment-108.40.8.192-20120821170323

I'm pretty sure the mision there is strictly "need to know." Nightwing probably came up with it so obviously he would be in on it. Aqualad is the mole/spy or whatever, so he has to be in on it. Artemis is in disguise, also has to be in. And you really wouldn't want Wally to seriously freak out about the death of his girlfriend, so he's in too.

The fact that Superboy and M'gann don't seem to know anything about this mission hints that, it isn't a trust issue, it's just they don't specifically need to know. The more people fooled, the more the Light or whoever will buy it.