Flat Footed 3year old (Advise Please)?

Just recently my mother pointed out to me that my son is severly flat footed. As leg problems run in my family i would have thought his pediatrician would have noticed. Leg problems run heavly in my family and my younger brother is flat footed as well. My mom told me the best thing to do is either get arch support insoles for him or get him a decent pair of athletic sneakers with a good arch built in. So i have now spent almost 3 days searching for a good pair of shoes and still have no idea what brand is best. He also has very wide feet for such a little guy. Any advise on good arch shoes for kids or even some good advise for flat feet or support on this topic would be great! (please no rude or unwanted comments thanks)