Editing the tags constitutes an "edit" so far as Stack-Exchange is concerned, and that means that editing tags causes the question to appear "active".
In general though I wouldn't worry too much about it. The list of active questions will change over the next few hours, and besides, there are other (perhaps more useful) filters that can be applied on the questions anyway, such as listing by "newest" or by "unanswered".
If an edit is warranted (and retagging edits are useful edits too), edit the question. Don't worry too much about whether it gives an artificial impression that the question is active. If the question was active before, it just shuffles the list a little bit. If the question wasn't active before, it's bringing a question back to public attention.
In either case, the value of contributors making real and useful edits to posts, whether the posts are old or new; answered or unanswered; content or tags far outweighs the downside of you "dominating" the active questions page for a few hours.