One thing I don’t hear being mentioned is your/ your wife’s extroversion levels. You describe a loving family life but not much about any friends that you will miss.
Sometimes a geographic change helps to boot introverts out of our doldrums and force us to make new friends. But sometimes we get to a new place and just sit in our living rooms waiting for them to drop out of the ceiling.
If you two are not the type to take a pie over to the neighbors or start a chat with another couple while golfing, then you will probably be lonely and isolated in a new place at this stage of life. A good test - do you currently correspond or keep up with anybody you have met on your travels?
The other concerns I might raise have already been discussed. I recall in the early 90’s a problem with Navy officers assigned to Hawaii being on food stamps there. It was not an assignment people wanted for that reason.
Do you see yourself moving to a smaller home even if you stayed in the Chicago area? If so, I’d say sell the big one now and get rid of the furniture. Be realistic about the possibility of getting a condo in a retirement village upon your return. I def do not recommend retiring in Hawaii where you have no family to check in on you.
The last thing I will say is this: T’were it me, I would not leave my Grandkids during the formative years. They will never again need/enjoy you as they do now. In the end, happiness is all about relationships. Weather has very little to do with it.