Our in-laws were both thrilled and disappointed when we decided to move here. They understand the amazing opportunity it is for us as a family, but they (obviously) miss their grandkids. The couple of months before we moved, they took every chance they could to be with the kids, and have already planned a trip here, and we are going to surprise both sets of parents by offering to buy them airline tickets to come see the kids once a year (on top of any flights they want to pay for themselves), and of course, we will be going back to Sydney and Auckland to see both sets of parents as well.
At the moment, we send emails almost every day with photos of the kids, and a phonecall home once a week. Once we're settled, we'll be setting up a weekly session for the grandparents to watch/interact with the kids over the internet.
I think as long as you explore all the options, it can work. I know my in-laws miss having the kids just down the road in Sydney, but I also know they'll make the most of it when they do see them in real life, and we will make sure they share as much of the kids experiences here as we can offer them.
Good luck with everything... I am sure it will work out.