Inner Circle
Forgive me for being a touch more pragmatic but perhaps it would be simply easier to strike where we can, irrespective of age or experience. It stops a pattern from forming. True, it is likely to force those who remain even further down into whatever boltholes they possess but that can work for us as well. Vermin do tend to huddle in a mass when frightened.
There is also the consideration of using this knowledge the Dark Lord has discovered, especially in terms of those among the DMLE. We know who they are. In any future attacks, we may be able to plant evidence that points to them. It could muddy the waters very nicely.
Also, we should consider letting the knowledge of the existence of an unknown vigilante group become public via the media. The suggestion could be made of the curious fact that this vigilante group has been active during the time of all these terrible attacks and that perhaps the two are connected. This would turn the DMLE's attention towards the vigilantes and away from us thus creating difficulties for Longbottom, Podmore, Bones and Moody. They either investigate their own and attempt to muddy the waters, potentially drawing the attention of unaffliated members or they risk being discovered and prosecuted.