I always think this kid looks so cute and cosy. The King Cole Cottonsoft DK, despite being a cotton, does have a slight fluffiness to it so it makes it warmer, softer and also easier on the hands. If you are worried about working with cotton it's a great starter. I would say this is one of King Cole's more complicated lace patterns, don't let it put you off but make sure you have an easier project on the go too.
I think it'd look great in the spotty King Cole Cottonsoft Candy DK too but I think I'd avoid the striper versions, as gorgeous as they are. With this being a kids thing too it would be remiss if I didn't suggest the Cherished DK.