I haven’t dealt with this particular peccadillo, so this is all just lip service on my part – but here are my thoughts…
You know, I share all these kinds of photos with STBX without his asking. Mostly because it means a lot to my daughters that he see picture of them at their various sports and other activities. It’s also how I handled the tricky Birthday situation – I gave him an album of picture of the girls (and from the girls) – the fact that these photos show the girls having a great time and going through significant life milestones without him? Well if that causes him a moment’s thought – that’s a bonus. By the way, I have never expected, nor received a similar gesture in return.
As far as cake eating goes – I dunno- I think you’re getting a little in the weeds with your definition. If she expected to go on your vacation with you as though nothing had happened – that would be cake eating. But getting copies of pictures? That’s parenting. And FWIW, no matter how your situation ends up, you’re going to be parenting together . Also- it would be one thing if she expected you to put together a scrapbook, but sharing phots? Pretty painless. Just send her a link to an online site without comment.
As far as the “she’s still in an affair- why should she get to do things like this” question. I will leave you with this thought. There is a difference between being the lighthouse, and being a towering statue of righteous and indignant judgment. I don’t think every interaction with our walkaway spouses needs to be agonized over , but maybe when these questions come up, ask yourself which one you are being? I think being the lighthouse includes a certain amount of graciousness, no?