But is HE paying you support? If not, what's the reason?
And yes, generally making a better life for yourself and your kids is something the courts will consider a good reason for relocation. I don't know what kind of relationship you have with your ex, but I got to maintain quite a good relationship with my kids even though we lived halfway across the country from each other. Their dad and I split the cost of my coming out to see them, and he kept me updated on all their activities and other important details.