I am a big fan of GAPKids - i think the clothes are great quality, comfortable and well designed. They wash well, the sizing is spot on and the designs are fun.
I recently went to the launch party for the GAPKids + Peanuts collaboration and i loved it, the clothes are awesome and the prints are bold, colourful and happy.
Here are a few of my favourites
GAP do great Sales and its worth signing up to their newsletter too as they often have money off events/ codes.