There are two issues going on. One, there are accusations passengers were over served and were generally disruptive. The OP did the right thing and contacted DL, which took that complaint, so there's no issue with the follow-up there. However, the OP asked DL to proactively contact two other passengers about the situation. This is not only meddling on the part of the OP, but initiating contact at the request of another customer is certainly not respectful of the other parties' privacy.
It would only be appropriate to initiate contact of the other parties based on the reports of the crew and/or a full investigation.