Each person has to make their own decision whether to kill the wasps or let them be. Having someone in the family who has a severe allergy makes the decision a bit easier. Watching the ambulance take a family member away is never pleasant; I know this from personal experience.
One other option is to learn how to prevent the wasps from building their nest on buildings/structures/in sheds, etc. Even though these suggestion won't work for nests build in trees, there are several good suggestions on this site about wasps building nests inside of bluebird next boxes. All seen like good, workable suggestions.
http://www.sialis.org/paperwas...
