Janet,
I do understand the toll construction can do on the body. I have a couple questions. Is this a shoe-in? In other words, does Tony have the job if he wants it based on Jamie's recommendation? Are they offering him a full time job with benefits or is it a "as needed" kinda thing? I think that last question would be the most important to me.
Knowing the area where Jamie lives, I know that you have lots of rural areas around there even thought you are moving north, I'm sure there are some reasonable areas to live.
Were I in your shoes, I think I would have Tony go up for a couple months and check out the job. He would need to see if he likes it, get a feel for the folks he is working with, perhaps look around a little for a prospective places to live, etc. I wouldn't make the move without a trial first. There is no sense making all the changes necessary to move to another state without being sure this job is something Tony can live with.
That would be my suggestion. And, change is scary but can also bring renewal. You would be able to form a closer bond with your other grands, start fresh and new with Tony, and leave Billy and Cory to take charge of their lives alone. Those are all good things.
Tough choices. You will know if it's right - so will Tony if he does it on a trial basis.
Sharon