The short answer? Yes.
While it’s against both park regulations and the law, thousands of people have snuck ashes into Walt Disney World park to scatter them in assorted places including the Dumbo ride and the ever popular Haunted House ride.
This great article from Gizmodo goes into detail about this super interesting Urban-Myth-Proven-True.
Remember, the best option is to talk to a professional ash scattering service to ensure that everything is handled professionally and legally.