I completely empathise with you over Christmas. For the first time I will also face a dilemma that has not happened previously even though this will be our 4th Christmas w/o H. Now that my S16 lives with H and OW and he rarely comes to see me (unless he wants money) I am not sure who he will want to spend Christmas day with. I have already invited him here but he has not yet given me an answer. Although it has been hard w/o H the last few years facing the possibility of not having S16 here as well is beginning to eat away at me.
Like MMF I too giggled at the comment your D7 made about morality. A couple of years ago when my nephews (on Hs side) were just 3 and 5 I was babysitting whilst their parents went to a wedding. The 3 yr old asked me is S16 was 'the daddy'. I simply replied 'No uncle A is the daddy'. His older brother thought about it for a while and then said 'If uncle A is the daddy why does he have a girlfriend'. W/o becoming very emotional and risking having to explain to very young children, who aren't mine, the intricacies of separation and D I just replied 'that is a very good question N5 but unfortunately it is not one I have the answer to' (I was very tempted to add that he should ask his uncle to get the answer but I restrained myself). So yes it is surprising how quickly children pick up on values.
Me 43 XH 45 M 2.7.88 Divorce 7.10.09 Kids D20,S17 & D15
