First off, disclaimers: 1. I'm new to the understanding of FLOSS. 2. IANAL/IANYL. 3. I can only give my opinion based on what I read in your question.
I'm going to say that there is nothing for you to do. You are "running"
PM2, and you didn't say anything about distributing it. AGPL 3.0, Section 2 appears to cover this:
All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met. This License explicitly affirms your unlimited permission to run the unmodified Program. The output from running a covered work is covered by this License only if the output, given its content, constitutes a covered work. This License acknowledges your rights of fair use or other equivalent, as provided by copyright law.
In addition, since you are not modifying it, only running it, you don't even have to accept the license at all. C.f. AGPL 3.0, Section 9
You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.
Nothing in your question suggests you're doing anything which would trigger any other sections of the license. So, I don't even see that you have to tell the users that you're using
PM2. The users only interact with the services it controls, so they aren't using
PM, and have no contact with it at all.