I do know toucans are omnivores, they predominantly eat plants but occasionally eat animal protein like live frogs, bugs and small birds. But i wonder if it's safe to have both passerines (up to 10cm in length) and toucans in one aviary? How to make them not eat passerine hatchlings?
It depends on the species whether they will be a danger to adult passerines. Aracaris have been maintained in aviaries with small birds with success by many facilities, Brookfield Zoo has them with honeycreepers. The small birds breed in open cages with doors too small for the toucans to access afaik.
I'm not quite sure what your point is here - toucans are also tree hole breeders. They are also documented to steal young birds out of cavity nests using their long beaks. Mynas might work a little easier since they are boisterous and pushy themselves, but there would still be risk in breeding them.
The smallest species of toucans (like Aulacorhynchus species, Baillonius or even Selenidera) could be kept with adult larger passerines (from the size of a superb starling upwards) without predation risk, I think.
