Child asks awkward question about his soon-to-be step mum’s wedding

How would you handle this?

A mum has posed a question on Mumsnet after her soon-to-be step child asked a rather tricky question. The mum explains that while her partner and the child's mum get on well, they're not great friends and she's not invited to their wedding. However, now the child wants to know why his mum isn't invited to the wedding, and she doesn't know how to answer it. She said:

"Me and DP are getting married and his DS asked me the other day why mummy isn't invited. He got distracted before I answered. "How would you answer this? DP and his ex co parent well but they aren't overly friendly and they don't really like each other outside of talking about DS. "I get on with her okay, no dramas or anything but nothing more then a chat at drop off/pick up kind of thing."

The mum went onto mention that the child is only 6-years-old, so many mums replied to her with suggestions. One of the most popular answers were:

"I’d probably go for something like ‘well, your mummy and daddy get on really well and do an awesome job of looking after you, but weddings are the kind of party where you only invite friends and family you go out and have fun with. It doesn’t mean your mummy and daddy don’t like each other though, just that they’re friends in a different way’ or something like that."

While another wrote:

"Ask him if he's worried about mom not being there? Then you can tailor the explanations to fit whatever's on his mind eg logistics of the day, mom isn't cross that he's invited and she is not, it's just for the party and everyone will be back to their usual routines afterwards, etc. "As he is 6 y/o, he's possibly just thinking about himself eg who will make sure my dinner isn't yucky/take me to the bathroom if dad and OP are busy with important 'wedding' stuff and mom isn't there?"

How would you handle the situation?