I only have one donkey, so I can only speak for him, and he's a gelding... When my mare foaled, one of the first things I did was turn him out with her and the foal. He never bothered either her or the foal, and she seemed to like his company. He's kind of at the bottom of the pecking order in my herd, but is protective against coyotes and unfamiliar dogs, which is why I put him in with them.
Here's a May picture of the 3 of them. Gus, the donkey, is just starting to shed his winter coat, and it's also wet from the rain, so don't mind his shaggy 'do
