The Heathcote Bootery has the largest selection of EXTRA WIDE shoes for kids that I've found. Two of my children wear orthotics (one has ankle splints the other arch supports) and require very wide shoes to fit around them. We were actually recommended to Heathcote Bootery as they specialize in fitting shoes around kids orthotics.
I've found them to be wonderful to work with. They have been great with the kids and I've always been amazed that I actually have a selection of shoes to choose from. At other shoe stores - even with the top name brand shoes - they often only carry one style in an extra wide.
I've also found the prices to be very reasonable ...... I've been spending much less on kids shoes since I've started shopping there instead of the shoe stores in neighborhoods near where I live (lower Westchester).