My kid has huge feet too. He couldn't wear regular Robeez after about 15 months because the elastic left big red welts on top of his fat little feet. So we moved on to structured Robeez and then Stride Rite. Most shoes don't even fit him because his feet are so wide, but we've had good luck in Stride Rite wides, See Kai Run and Keens. And since I tend to have great luck finding second hand shoes we've not gone broke.
Honestly though he walks a ton with me when we are out and about. I don't think that Robeez are really made to go miles a day on pavement. When we are at home he wears Hanna Andersson leather soled slippers (and now that it is getting warmer he can go barefoot more).