We saw this show 2 times, once in Indianapolis and again in Des Moines Iowa.
Loved, loved, loved the show.
Going to the theater IS a big deal for our family, we try to go to a nice production 1 time a year. We treat it as a special occasion, and try to dress a "nicer than casual". I try to keep in mind that I will usually freeze at big theaters, so I make sure that I have on something i.e. a twin sweater set so I won't freeze, or can take off the sweater if I am warm.
As far as dress goes, we do keep in mind that if we see a production in a city like Chicago, we will be walking lots, so what we wear needs to be "walking friendly."
Wear what is comfortable for you. Yes...shorts to tuxes is the range.