In my case I do everything I can. My son is 6 but he's put me on the spot with questions about his mum which if I answered truthfully would probably upset him.
I try to tell the truth without saying anything bad about her.
I encourage him to make things for her while he's with me, talk about her and have a picture of her in his bedroom and have said if he ever wants to talk to her, etc. while he is with me he can do so whenever he wants.
Because she's his mum and he loves her and I don't want to upset him.
Stop coaching him. I know it is hard but you have to let the DC have their own relationship with him and you have to stop trying to make it better.
I've been separated for 10 years & divorced for 8 and I spent years trying to ensure the best relationship for the DCs & ex-H. My two are early teens now & they've worked out for themselves that he is a selfish arse, who doesn't really give much of a toss about them. That is despite all the polyfilla I spread around liberally to fill all his narcissistic cracks. It was a pointless exercise and a waste of my emotional energy.
My advice would be to step back & let him & them work it out for themselves as much as you can.
Ex and I split in Feb 2013 after his EA and affair. We have 3 kids ds1 (12) dd (10) and ds2 (7)
Ds1 has been affected most by XH's EA but is his favourite child. He loves his dad but fully aware that he is EA and a selfish twat (his words) Dd is his biggest fan and has inherited the best parts of him but IMO she will never become number 1 child because she is a girl. Ds2 is indifferent to him and is often overlooked for ds1 and dd. I had to tell ex to get him a birthday pressie where as he often gets gifts for the other 2.
The kids "know" that ds1 is his favourite. Dd tries hard to please ex but I honestly think that as a girl she has no chance of being adored. (Obviously Id never tell her this!!)
Do I tell ex that he is being out of order treating the children differently? He did this while we were together but it's never been obvious to the kids. I am sick of coaching him in being a Dad and he probably won't take kindly to me telling him what he's doing wrong but I fear that the current situation will lead to self esteem issues with dd and ds2 and resentment that ds1 is the favoured one.
He sees dd every Fri evening to Sunday afternoon and the boys once a month form12 hours. This is the amount ds1 and dd want to see him.(Ds2 would prefer not to see him ever but I make him go)