L.S.
I would recommend going to the National Museum of Mexican art (free!) in the Pilsen neighborhood, particularly during Halloween/Day of the Dead time when they have hands-on exhibits for the kids and you can watch how they make the candy skulls (I think there are even times when families can participate) and have your name put on your very own colorful candy skull. From there you could go eat on 18th street - the restaurant Nuevo Leon is very well liked.