If I were you, I would buy mostly 000 and a few 0000, because they are in them for such a short time. And if the 000 look too big, you can roll the sleeves up and put socks over the outside of the jumpsuit to hold the feet in place. It really isn't going to matter if their clothes look a little big to start with, especially if you're on a budget and can't buy too much to start with.