XH and I divorced 8 years ago, we have twins together, DD & DS(12) and it's a miracle if he phones them up on special occasions let alone spends time with them.
Around Easter he phoned up out of the blue to tell them that he got married 
no explanation as to why they weren't invited or told beforehand, it wasn't even a surprise as they saw the wedding pictures all over fb, thankfully neither of them seemed too hurt/disappointed, I got remarried years ago, so they've had an active step dad in their lives, which I think has massively helped deal with the twat that calls himself their father.
Surprisingly the phone calls became more frequent after April & I thought perhaps having DSC in his life has made him realise how important it is to be a part of his own children's life.
Then at the beginning of June, he asked if he could come over one weekend and see them, he hasn't seen them in 3 years, so I agreed and it was a complete car crash.
They spent the day in the garden, he'd bought DS a football shirt as he use to play on a team as a child & DS piped up & said no, it was in fact DD that played & that he hates football. He got DD a 1D shirt that was far too small and she looked like she was going to throw up, she's more of an All Time Low fan.
He'd bought a cake that his new wife had made and had to be told that the twins were allergic to egg. DH and I devoured it instead, it was bloody delicious 
.
Lot's of eye rolling and huffing from the twins before he awkwardly left, I was sure that was going to be the last I saw of him, but he phoned two weeks later and asked to take them out 
It turned out to be for a family barbecue, so XH's wife, DSC & aunts & uncles that the twins haven't seen in years. They said they wanted to go, so I let them & they were complete brats. They were sarcastic & rude and spent the day complaining, they came home by 6 & the barbecue only started at 3.
Haven't heard from XH since then, until he phoned this afternoon. He & his DW are planning a camping holiday in Cornwall with her DC & wanted to invite along my twins .
I said I would ask, but I already know what the answer is going to be. My DC are sadly not country loving kids, they abhor anything that makes them uncomfortable & endangers their phone signal, camping would be at the top of their never ever ever doing list.
But, a week of uninterrupted time with XH could be just what they need to try and build a relationship & it's a week of free childcare over the summer 
Would going be beneficial to them at all? Or am I fooling myself into thinking that this is for their benefit & not my own?