DS has worn xw width since his first pair of shoes and he's almost 4 now - everybody told me his feet would thin out when he started running - his body did but not the feet.
We started with stride rite, but too often they wouldn't have anything in his size at the store and sometimes not even online. So now I just buy New Balance from Amazon. I buy the next size up when his get a little snug. I've given up on ever finding dress shoes for him so I just buy a dark pair of the New Balance.
DD is 10 mo old and I just measured he feet last week... she'll be in an extra wide when we move on from robeez. I just "won" her first pair on ebay (stride rite).