I still didn´t get t he usual dialog with Big March, but I can confirm that you can just straight walk to his father and close the quest.
However, I was forced into fighting Peeper. IIrc in vanilla his father gave you a choice, kill Peeper or refuse, now this dialog doesn´t even come up and according to the questlog, the game treats it like I have refused.
The fight is easy though and I got alot of source orbs out of it, still not sure if this is intended.