I don't quite see the trap: if you want to leave, why don't you leave? Seems there are plenty of opportunities out there.
Having a raise is an incentive to stay, not an obligation.
The question is, does your family really _need_ your current salary or is a lower salary + happy dad better for your family?
If you want to make it easy for them to replace you, automate and document as much as you can? That way, if you want to leave, you can just hand over the job with only a few days guiding the new person around.
mining boom won't last forever, in fact, I'm not even sure if it's not over already. Many mining companies went bankrupt recently. So squeeze as much as you can while the opportunity lasts and when you lose your job, start your own business. you should have enough saved up by then.