I know your question was for Michelle - and she and I might differ on this - but I think you should not extend that an invitation to your W to join you guys. Maybe say something like, "hey, if you want to join us, that would be cool too" - but I would not make it an outright invitation...Stuff that would make so much sense in a regular relationship just feels like clinging to the person that it questioning things. That said, I believe only you know what is best for your situation - and so I think you should follow your instincts. If you know that asking might push her away, and you're okay with that - then may it's fine to ask - if you know that asking might push her away, and you don't want to risk that...than focus on you and your boys.
Sounds like you're planning on a great time with your boys. I just dropped my oldest son off at an indoor rock-climbing camp...he could not be more excited...
