My daughter's SM has completely different interests to me. I'm more 'natural'; camping at festivals; classical music concerts; live quite simply.
She is 'glamourous'; eats at Michelin star restaurants; hotels; listens to pop music; video games... We couldn't be more different.
My daughter looks like 2 different people at times - when she's with me, she's all jeans, festival t shirts and DMs yet she can apply make up expertly, can name all the best restaurants in town...
I can choose to be cross that she has an external influence that places value on women's appearance and materialistic preferences (both of which I have huge issues with personally) or I can choose to think that it's a positive thing that she has someone in her life who cares enough to want to do these things with her.
My ex is, quite literally, a Disney Dad and I have internal eye rolls regarding many things to do with him. But it's just a different way of doing life and it won't hurt my daughter to have different experiences that I wouldn't give her.
You really need to chill and get on with it.
I wonder how much different your son's attitude would be if you said, "Park Run?! Wow, that's brilliant. Fancy that. Have you earnt your running shoes yet?" Because your negativity will be influencing him and that's not fair.
I could understand if you were saying they were doing nothing but playing video games and eating nachos all day but something that is a positive - developing fitness - is something you should be encouraging.