(Long time lurker - first post)
The course I would suggest, if on the IPW, would be to rally the Human fleet to set up a redundant and tamper-resistant self-destruct system on the newly-discovered star - with a similar system set up at the Human colony one jump further back.
When the Super-Happys return, we would give them the option:
1. Altering their preferences to align with Human values, at least enough so that they would no longer consider changing Humans without their full consent.
2. Immediately detonating the star - so they would no longer be able to rescue the Baby-Eater's Babies.
Any other course of action, or attempting to tamper with the self-destruct would trigger the self-destruct (and perhaps that on the next Human Colony in case they prevented the first nova).
We would offer volunteers to join the Super-Happys, in order to explore the feasibility and desirability of further harmonization. (and also monitor their compliance with the agreement... and steal as much technology as possible).
I say this as an unabashed defender of the superiority of Human values, who is willing to use our native endowment of vicious craftiness to defend and promote those ideals.