Then, what's the problem?

You either move or don't, you can't win anything without doing anything.

It's not like you are bound to one place with some unbreakable bonds.

Why resentment when the agreement has always been there?

If it won't work out, it won't. You'll just have more experience and will be able to move back since you, admittedly, have immediate family here.

If your immediate family will be sad, well, tough luck, people are not born to entertain other people - you'll be one plane and a couple of hours by car away from them, if anything. Internet also exists.

In regards to your kid. It's not like you are a military pair who moves every now and then, at this point a child will have almost the same amount of stress moving to a different city. For better or worse.