|Heathcliff in a cake box|
I decided a long time ago that it was far easier to do myself than waste my breath assigning the task to the children. The children are better now and they will empty the trays if they notice. Operative word -- notice.
Heathcliff and Mr Darcy are clean cats and they require clean trays. Because I like the pine scent, I use the compressed wood pellets. It is just easier to deal with.