Shoes are so personal, but, if your stepmom thinks a dressy sneaker is an oxymoron, she might be interested in checking out some of the European comfort brands like Reiker, Naot, Arche, Mephisto, Finn Comfort, and Ecco. They can be a bit pricey, but spending $$$ on a trip and being hobbled by footwear has never made sense to me.
I can personally vouch for the the Mephistos--not the most stylish shoe, but they served me well from dawn to dusk on a 4-week vacation in London, Paris, Prague, and Budapest where I walked constantly for 8-10 hours a day.
My Munro sneaker style has also been a walking workhorse.
