Moody volunteers for the super sekrit order bit. He wants some action, hexing people or whatever that mission will entail. Sitting in a safehouse 24/7 is boring and you can only read so many books for so long before you go spare.
Charles volunteers for the DA attack. He promises that his muse will get his portion done this time.
As for Rabbit, he volunteers for the Macmillan attack assuming not all the spots have been filled so far. This is because he does not want people listening into his life, what would no doubt be perceived as yet another failure for him.
Arthur's muse desires for him to be recruited by the Order in the near future. More pain and suffering sure but it will be healing (lol) to fight back against these crazy people.
I will be here for the battle but I have a wedding the weekend of October 10th so my logs would need to be done before then.