"Honestly. Stop pacing before I charm your shoes to the floor." But Peter doesn't really mean it and there's a kind of exasperated fondness in his voice. He's a little tense too because he's aware he's sitting on a powder keg with these two. He doesn't care about the Strider much, but he wasn't kidding about being horribly fond of Murdoc, and he dislikes the sniping and arguing and continually bringing the children into it. So if he has to sacrifice a bit to get them to stop, so be it.