M.H.
Crazy 8 seems to run larger on my son (which I love)! Right now, my son needs to wear a 5T in Gap, and at Crazy 8 a 4T fits fine. A 6-12 will probably be too big, but you can always roll sleeves up if need be.
P.S. It is owned by Gymboree (not Children's Place), so if you have any of their clothing, it runs like that.