I'm not sure that there is a "correct" way other than following your sense of ethics. David DuChemin talks about this in his book "Within the Frame" and I think photojournalists/documentarians face this all the time. I've tried the 70-300 mm on groups of people on a street and have not been happy with the results. And it has nothing to do with ethics. I find that to capture the "flavor" of a place, I need a more intimate lens. And actually, some of my nicest shots are the ones where I've asked someone to hold a particular pose and snap a couple after they drop the pose. people are really interesting to photograph, and for the most part, pretty gracious about being photographed.
So, in answer to your question, no, I don't think what you did was in bad taste. But you should try it both ways and see which gives you the kind of photos you want.