Most family estrangements if they resolve / reconcile do so after 7 years.
Reconciliations may vary tho and it might be just being able to be at the same unavoidable event in a civil and polite manner. No going over old ground. Water under the bridge.
It might mean keeping a personal distance but supporting the children to understand conflict resolution and new ways of interacting.
I wouldn’t factor MM into the picture at all - she’s already in the departure lounge - she’s not going to be involved or seen in public in the UK.
PH and the DCs will
seek to continue their private relationship with KC3 and hope to extend to rest of RF in time.
Whether KC3 and PC invite the children to Christmas concert and Sandringham walk will be interesting. I think both are softer and would have some compassion for all the DCs impacted by this and want to avoid accusations of exclusion of their own grandchildren or nephew/niece when loads of other children are there.
But it could be that it’s only PH and the DCs and that MM is ‘not available’ as filming a blockbuster on location (or some other excuse).
That arrangement would suit MM
as she is a coward as most bullys are and she would still personally benefit from the glow of the royal glitter from her DCs and STBXH.