It will be hard. There is no denying it.
I must be honest and say that I could never choose to move away from my grandchildren. However, my eldest daughter went to the US because her husband got an extremely good job offer. Parting from them and their 4 kids was incredibly hard. We keep in touch through technology, of course. However, to be truthful, it is not the same and I never stop missing them. If I didn't have my other grandchildren living nearby, I don't think I could bear it.
On the other hand, my grandkids are 4,000 miles away and across an ocean whereas you will be 500 miles away and, presumably, in the same country. You can visit, they can visit, and you have the excitement of the new place and new job to occupy you. It is harder, I think, for the ones left behind than for the ones who are off on a new adventure.
Sorry if this is a bit negative. I don't mean it to be, but there's no point in pretending it is easy. It will take time for you and them to adjust.