My sympathies, smartie. I have an X just the same.
I take comfort from knowing that my DCs will remember how I cared for them and their Dad didn't. Children have a strong sense of justice, in my experience, and the care and love you show them now, however exhausting it is, will forge really strong lifelong bonds. Stay strong, don't get bitterness sap your energy and remember your X and mine has chosen to throw away one of the most precious gifts in life, true love and respect from their children.
I'm big on karma.
In the meantime, buckle up and have a and several [biscuits] on me.
My son's just got better after 3 weeks of virus after virus. He's gone to his Dads for the first full weekend in a month, I'm so looking forward to sleep! Still, it was his choice to stay with me when he was ill and not go to his Dad's which as freaky says is a testament that he has a real bond with me and din't really want his Dad.
Try not to waste your emotional energy being angry at the ex, it won't change the situation and they can't feel it so it's only you being negatively affected. Be thankful to yourself and the grandparents that you're not so selfish, praise yourself for being responsible and loving.