Sorry, but I don't believe his invite is in any way a step toward reconciliation. I think he is simply ahead of you in the game. It's possible he did all of his "chewing" on the state of the sitch during the years prior to the bomb. Since then, he's been healing, looking to his future "after the D," as I believe you put it. I would guess he just doesn't want to be enemies. It takes too much energy and effort, plus even a social idiot can see that's not good for the kids. It's likely he put very little thought into the invite, whereas you're racking your brains over how to respond. You're at the end of his whip and he probably doesn't even know he's cracking it, or least probably isn't doing it on purpose. (This is coming from years of experience with my H's exW, and her being completely unmoved/unaware of the chaos she sowed in our life.)
I think the time off of parenting is reason alone to stay elsewhere. I commend you for doing this with the kids. Focus on you, focus on them, don't worry about exH's response.
