That took care of a good number of the hornets/wasps, but several hours later we kept seeing them flying around. The house next to us is currently empty and has a shed in the backyard, adjacent to our backyard. I went around the the shed and noticed several hornets/wasps coming out of the shed. Fortunately the shed was unlocked and I opened it up and found five more nests of similar size. Yikes!
I think we've taken care of the problem now as I don't see any flying around our backyard now. It was an interesting adventure. My 6 year old was particularly interested in the nests, which admittedly are very cool in the absence of hornets/wasps! She was so interested that she wanted to be part of finding them in the shed, but I had to put my foot down and tell her no on that one! Too risky! In the end we knocked out eight nests of similarly large size and no one in the family was stung! Now that is a success story!