I believe Mach40's daughters are 21 and 31 so there isn't any official custody agreement stating every other year birthday or split Christmas...etc., and his wife got her own place just a year and half ago so they don't have any typical rhythm from years of divorce which they can fall back to. Do I remember correctly that your daughters live with your W? That might further complicate things, giving his W the "home advantage" and having Mach wanting to keep involved.
It really is up to Mach and his daughters at this point to arrange some sort of split for the holidays if he wants to change the dynamic.
Me:39 Ex-W:37 M:7 T: 9 S:6 D:3 BD/IHS/Confirm EA/PA: Feb '20 OM1 affair ends: May '20 W/OM2 & moves out: June-July '20 W files for D: Jul20 OM2 confirmed: 9/2020 Divorced: May '21