I suppose what I wonder is, where did the idea that balloons are emotionally significant come from and why that? Why not something else? So, what are the harmless yet emotionally satisfying options?
It certainly wasn't long ago that balloons began to be used. In my childhood, 70s - 80s, I only ever heard of them being used, with labels, in 'balloon races' which were a bit like messages in bottles, competitions to see which could travel the furthest.
Balloons seem to have been popularised, along with fireworks and less often doves, as an 'extra novelty' at weddings primarily but other events too, as part of the capitalist expansion of weddings really.
I suppose I thought placing flowers on a grave was the thing to do and what I've done myself. Results in dead flowers but, they do rot. Planting things seems more positive - but where they're wanted, not by scattering seeds where they'll never thrive. Planting commemorative trees is a little more problematic, as they don't always survive. Some charities will let you sponsor an area of woodland, lay a plaque for you, read out a poem, but not link it to a particular tree. I think contributing to the upkeep of a particular site; a nature reserve, park etc would be lovely, as you can always go to that place and remember.
Incidentally, scattering ashes on mountains and in other wild places is a problem too. They change the pH of the soil so kill the plants the place is special for.