Allow me to barge in as the child of parents who both ‘did over’…
Yes, your needs count, but always in conjunction with the kids. You seem to have a grasp of that.
Have you calculated the impact on the kids from being away from their mother at this age (whatever age it is)? It can be significantly painful, confusing, and/or damaging if they lose a good parent for most of the year, especially if they do not grasp the concept of time completey (before, say, 6-7 years old?). Summers and holidays are ‘nice’ but they don’t permit much in the way of long-term functional impact as a parent.
Can your do-over involve a long-distance relationship for now? LDR is rough, but so is long-distance shared custody. Rough should be on the grownups, not the kids.
Family nearby the new location is a definite bonus, but must be measured against the loss of mother. Age, again, is a factor.
Methinks from the wistfulness of the OP, that you already know the answer. You wish wish wish that you could just up and start over, and that it would not have a significant negative impact on your kids. You hope that someone will tell you that you can have what you dearly would love to have. It would help you put aside your concerns if other people corroborated your dream, rather than your underlying discomfort about the impact on your kids.
Sound about right? I’d trust your gut, not your heart. Does your gut say your kids will thrive on the move? Not survive, but thrive.
Work it out over time. Yes, you may have a more limited window because of the distance. But as you work it out over time, you may discover that it will or will not enhance your children’s lives to have this other person in your life, too. And if it is enough of a positive, that may push the line to where a move is the right choice as time goes by. I found my step-parents to be valuable additions to my life. But the degree of value varied widely, too.
Long run, I ended up developing a good relationship with my dad (summer custody only), but he influenced me almost not at all as the non-major-custodial-parent. I didn’t develop that relationship until I was an adult, when I lived near enough to him that I encountered him regularly (proximity was entirely accidental, btw). The daughter who did not live near him still doesn’t talk to him - she hasn’t developed a relationship with him, period. Proximity is a powerful force re: frequency of contact, and frequency of contact is, IMHO, a major factor in developing a maintainable relationship with a parent. JMHO, there, no stats. But that’s how it worked out with us. We can ask Tranquilis if he had a similar experience with our mom - I believe that he began to develop a ‘real’ relationship with her when he lived nearby, too (he lived with our dad for most of his childhood, his choice).
Are we ‘okay’ as adults? Mostly. Definitely all needed therapy, and some of us had some mighty big disasters of relationships and funky issues. Not all from the parents, mind, but there.
Not sure if that is helpful, but hopefully it is at lest food for thought.