Hold onto the ashes as long as you wish Ric.ror. When the time is right and you can do what you feel is appropriate and would be desired by your mum - then is the time to act. In the meantime, I can't understand why you shouldn't take her to the seaside or any places she loved as a last tour.
I once taught a 13 yr. old boy, whose mum died one October. He was an immature lad and had a teaching assistant who shepherded him and helped him generally in school. She carried his mum's ashes around, in and out of classrooms, for the rest of the school year so that he knew that Mum was never far away. Do what you feel is right.