I still will invite the W to do things occasionally, but I'll give it a pause, before restarting that. And, I'll focus on doing more fun things with the kids rather than inviting her to just dinners.
I wouldn't say it isn't good for the R, as asking and being very casual about it still sends the message that I'm open to this no-obligations R that friends have. I think the DB coach is right on this. That said, it was getting me too focused on her, and I needed to change that so the dynamic would be better for both of us. She also said that she didn't think casual dinners was something right now. Great, back off, and try a slightly different approach. It is not that it was having a bad effect on W, but that it was clear that it wasn't joining us for dinner that would be on the menu in the near future. It was having a bad affect on me by not moving my focus more fully on me and my path.
All that said, I've been working for months w/ DB coach to - as she calls it - let the dust settle. The emotions, the tensions, the pressure, the reactivity. All of it. That has indeed happened. It hasn't meant a course change in the M, but it has improved the R enough that doing something like inviting W along makes some sense. A couple months ago, it definitely would not have been a good idea. So timing is important. Inviting S along is not either a good idea or a bad idea. It is all in the context of where your particular R is going.
I think you are a bit too early to worry about this from what you've shared, so I would just stick the idea in your pocket for later, and focus on the things that are already on your plate.
Me: 50 W:43 S6, S3 M: 12 yrs. T: 17 M is bad & Not happy Bomb Mar '14 S 5 Feb '15 D Bomb 13 Apr '15 (but "no hurry") DB Coach May '15 Wants proceed on D Aug '15 Starting 1-on-1 negotiations Sept '15