My husband and I have told each other what we want. OF COURSE no morose send off with lots of darkly-dressed folk. Instead, an organ donation, a cremation, and a send off by being planted or scattered under a tree. Bench donated with our names. Same as you.
My uncle was an atheist also and he had his ashes buried with a new tree planted in that spot. I loved the idea! His was an evergreen planted up in the mountains near their home. I like that because, eventually, the tree will die too. Seems kind of nice, really.