Cane toads are an ecosystem destroying highly invasive introduced species.
The crows are doing our work for us. The method might be messy, but cane toads should be exterminated in non-native habitats as expediently as possible.
Instead of feeling bad for them, why don't you feel bad about the species they have almost wiped out?
I feel bad for the native species. Cane toads are prolific throughout the world, and they've driven many species to near extinction.
At some point you have to decide what your priorities are and start culling. E.g. Australia wants to kill 2 million feral cats over a decade, as there are 30 million of them, and each one kills 3-20 native animals a day. [0] At some point you have to make decisions and decide which is more important. If you could teach crows how to eat cats, Australia would like to have a word.
I love cats, I have two (both indoor cats, I love Cats but they are furry little killing machines even when well fed) and I still think the plan is reasonable if sad, it's sad for the cats and sad for the indigenous animals that are suffering predation from an invasive very effective predator.
And the crows friends are watching the whole time too.