Ooooo, no, the 24" won't work if using the usual circular technic with the child's size in that pattern. It says it stretches to fit 18" - 20", and when you use circs, you need to have the sts comfortable go around the needle, with a little ease to spare. So if it were, say, for King Kong's head, with an actual finished circumference of 26", to stretch to fit 28" - 30", then, yes, a 24" needle would work. I'm not a magic loop user, but my understanding is that that works best on long circs, such as at least 32". So unless you have a set of DPNs in the right size, I think you are going to have to wait until you get the 16" circ. Sorry to be the bearer of bad news!