"I've made more than a few in my time, Strange," is what Childermass adds in regards to mistakes. He's as human as the other magician, ignoring the entire accidental faeblooded portion of that. After that, he's quiet for a tic or two, actually considering the offer, but...

"Just if you could go and make sure that Baker has been let out. I don't like keeping him holed up in that ridiculous little ball device but I couldn't have him digging up the entire carnival while we were gone."

Yeah, all he can think of is 'please go check on my dog'. Of course.