You should always give it a try for the status match. They were helpful in my case 2 times in the past for silver which at least gives you lounge access for your flights. Being SEN is already a good reason for them to match you, doesn't really cost them anything. Id say it's probably too late by now though since your flights are so soon.

Regarding your specific case with M&M be careful with the booking number and booking classes and make sure they actually earn something on M&M. There is a difference when you book with a M&M airline booking number or CX booking number as well. As suggested already, the best way is to add the frequent flyer number at a later stage when you already commenced your travel.