I'd back it up one step. You don't even know that she wants this -- you are just curious to know if she does or does not.
It sounds like a grand noble gesture to be all "I love you so much honey! Let's fling the door to this monogamy cage so you can be Open!" But that's just a grand gesture on your part to make YOU feel good right now.
On her end? How do you know she won't be offended at the proposal? Go easy. Nobody ever died from going slow. If she's changed her life so much? She could go the opposite way. "OMG! How dare you? I change all these things in my life to build THIS monogamous relationship that I value a lot together with you and for us. And you devalue my changes and what I have done by suggesting our marriage is a CAGE? And that I go fuck around? What the hell?"
So ask her if she still wants it first and see how she feels. If not, drop it.
If so, would she be willing to just TALK about an open marriage -- Open in Heart and Mind to YOU. If so, learn together.
And you can always worry about Open in Heart, Mind, Body, And Soul -- WIDE OPEN later or decide not to go there after all. Approach this TOGETHER and on the same page.
You say a lot of your stuff is "perfect." Cool. Does she feel same? Or not? Why?
How about all this:
- Our youngest is a 3 month old baby and both her pregnancies were hard. Is this the best TIME to plan an Opening? Best time to even ask her about discussing an Opening?
- What about conflict resolution? Is that good between you?
- What about general knowledge? Is that at the same place?
- Are we talking swinging or polyamory? What if you want one and she wants another type of responsible nonmonogamy?
- What kind of open relationship models are you two seeking?
- What is your agreement for how to be together in right relationship while dating? What's the saturation point?
- Have you both filled out all the things at http://openingup.net/resources/free-...om-opening-up/ and talked that out?
Do not answer all that to me -- talk to HER. There's still a lot
more to discuss with her if she's willing to talk with you and plan an Opening together with you.
Stuff to explore together: