My husband once asked if he could have his ashes bured under one of the bricks you can buy at the entrance. He did it just to freak out the CM( he has a stupid sense of humor) but the CM did not think it was funny and he said as his face turned white that it was not allowed.
I say don't ask, don't tell however there is a nice secluded spot with the wishing well that is beside the castle.. walk toward Tomorrow Land from Main St. Castle will be on the right. ON the right just before you get to Tomorrow land you will see a path, take it and half way up is Snow White's wishing well. If it were me and I was going to do this that is the place I would choose. OR if you want an even less traveled spot go down to the docks where the old swan boats used to run.
IF you ask me, once Disney gets wind that people want to do this it will not be long before they offer this service if the price is right for them. I say go for it. Also, I do not think ashes pose a health risk. If this is what your loved one wanted then I say do it .