HOWMAR said:
Before you decide on staying in Santiago proper, realize that the city of Santiago, as nice as it is, is a major city with over a half-million residents.
You might want to stay within an hour of Santiago, Peurto Plat for example, and experience one of the Dominican beach resorts.
HOWMAR has a point. If your son is done with his missionary work and is free to travel, you may want to go to Puerto Plata which is more of a traditional vacation spot. If you son needs to stay in Santiago and you want to be with him, then I advise you to stay in Santiago. Traveling to and from Santiago could be a bit troublesome for first time travelers.
Regarding the bit with wearing shorts. Most Dominicans adults don't wear shorts. Since Santiago is more of a business center than a tourist area, some of the Santiago residents (Santiagoans???) on this board have commented that only tourists wear shorts and if you want to fit in, don't wear shorts. (HB/AZB please correct me if that's not the gist of what's been said).
When I am in Santiago, I wear shorts in the daytime, slacks at night. Whereas when I am in the towns on either coast, I will sometimes wear shorts at night, even in the casinos. This dress code seems to be changing. Years ago, you were not allowed to wear shorts in some of the casinos.