Its a difficult one Kat. I hope you can work something out with your parents.
I am so lucky (only child also for my Mum) in that my mother has always been really supportive of me going off, travelling, seeing the world from as soon as I was able to go it alone. And that she and my step father are really supportive of us heading to Aus now (they always knew there was a good chance I'd end up there as married to an Aussie). Of course they freely admit they are gutted we are going but that they would never be angry or make things difficult for us. They appreciate our reasons for doing so. And say that if they were in our position they'd be doing the same thing. I can't imagine what its like to have parents who guilt trip or make life difficult because they are upset or angry about their child leaving. I appreciate pretty much every parent must hurt, but how they cope and deal with it is the key thing. Some seem to handle this sort of thing better than others.
I've always been open and honest with my parents and we told them 2 years ago we were looking to move this year or early next and have kept them posted as things progressed. I'm sure we'll have our teary moments in the months to come before we leave but I am confident I, we, still have their full support and am being as considerate as I can be re the move.
Once again, really hope you can find some middle ground that works for you all. Keep us posted.