We have gotten better at this over time. The last travel project, my 7 year old son ran, The Left Over Peso Project, where he collecteted left over Peso's from people who went to Mexico from his school for an Orphanage in Puerto Vallarta. We collected almost 50,000 pesos to help provide computers, and other things that were needed. Mostly now we just raise money, because that is what these on the ground organizations can do the most with locally. That and soccer balls and sometimes medicines.
Unlike most who go an never leave the resort, at least we are trying to do something, and if that brings a little joy to children, then sucess. Certainly on our first trip to a country at the level of development of the DR, we did not know what we were doing, or what to expect, certaily the DR is much lower than the average place we have since visited in Mexico. We also now try to work directly with some local agency, rather than something so random.