Thanks for checking with basenji people regarding suitability of basenjis as therapy dogs! While I have known of a couple who were used as therapy dogs, as a rescue volunteer, I've also taken in basenjis from families relinquishing them out of fear for the safety of their special needs children. Either seek an adult (over two years old) with the right personality or a carefully bred pup whose parents have the right personality. For the pup, correct early training is very important. Through my volunteer activities, I have had many opportunities to see the results of less than ideal early training.
I hope they are successful in finding the right dog for their family.