She sounds a bit bonkers but I'd jut ignore it and think what a idiot she's going to look when the 'relationahip' ends and she has to rewrite her profile to remove them
and i can guarantee that there will be many people on her SM also rolling their eyes at her newly acquired 'family'.
I wouldn't mention it again to your ex (although I understand why you did), he might well also privately think it's a bit much but not want to admit it - esp to you. If his family do think it's lovely, they're probably just hoping for a bit of normality and stability. And some people are just a bit stupid 
I'd second no longer facilitating it. Except for reasonable special requests, I don’t do any of the pick ups and drop off for ex. He chose to leave the family so seeing the children is on him. I encouraged my children to see him still when they'd had usual fallings out and were saying they didn't want to, as I would have been reconcilliatry were he still at home, but your ex isn't doing any of the parenting, isn't doing the picking up/dropping off, isn't even paying maintenance, so he's not bringing anything to the party that you need. Leave him (and his wonderful new partner...) to it.
My ex and I had regular (around 6 monthly) reviews of contact, dates, times, day to day parenting responsibilities, taking to clubs etc for about the first 5 years as both of our lives were in a constant state of flux and the children's needs changed. So it's perfectly reasonable.