When ds1 had swimming lessons as a baby it was dh who got in the pool , because he worked 90 hours a week and did bugger all else. I wanted to watch and see ds1 experience it but it was his turn.
However be careful about the faux "sadness" it adds extra pressure if a woman is struggling with body image. It's not bloody easy to equate the changes in your body after children with confidence. Yes it's the marketing ads, yes its crap that we should feel like this but some women do. It doesnt help when some bugger starts rattling on that you should get past it and make memories and all of that. It can guilt women into feeling uncomfortable.
Those women may do everything else, make memories at all other times , but the faux " ohhh but you're missing out " may well make someone feel even more rubbish.
Its not all about weight and we should have body confidence but doing the wide eyed pity crap is not going to suddenly create it for someone. How about being truly kind and letting people do what they need to.
I took DC swimming recently with DP and I was the only woman in the pool , the others all by the side. I am fortunate I've just lost 7.5 stone so I felt ok, of course that shouldn't matter but it does sometimes. I didn't pity the other women, they are dealing with their stuff and I deal with mine.
Basically just leave other people be , there really is never a situation where it is ok to fake pity or fake shame people for not being as enlightened and confidant as you. Just leave other people be and get on with your own stuff.