There is certainly nothing keeping him from being ready to go. There is a part of Lucius that is analytically curious about this new Severus Snape, watching the process of how one does set about planning the murder of idiot thugs and how much enjoyment he might glean from it. Not much, turns out, and that's a thing Lucius can appreciate. He's had enough of hopelessly sadistic colleagues and, indeed, overlords.

Which isn't to say he might not will absolutely spirit out a little enjoyment from the whole affair, but he is his own lost cause and doesn't count. He can trust himself not to be Bellatrix, in any case.

Beyond a few fiddly questions about logistics and other curiousities, Lucius requires nothing but his wand; he follows.