Kate would be all for this. Just tell her where to stand and when to go, Arthur. You definitely already earned her trust, and in this case, her loyalty. c:

Jo would be a little harder to convince - not so much when it comes to Arthur or anything, but more so that she'd probably check to see what her mother and the rest of the TFW fam is doing. If she thinks she's needed, she'll definitely help out, but she wouldn't jump at the opportunity unless her mom or Sam or Dean were already all for it.