Aww that’s sweet! Initially I wanted a retreiver but then I read they were trained to carry birds in their mouth and didn’t want to risk it. Sounds like it worked out here!All our family dogs have been trained to be gentle with other animals. They are trained to retrieve but never harm. We have found that the best way to train is from a young age with lots and lots of socialisation. My personal method - give everyone a BIG afternoon play so all the excitement factor has been worn out of them. Then after dinner we have quiet "combined family time" where all animals are supervised together. It's a gradual scale of introduction starting with everyone on leads and/or in cages close by and eventually with everyone just being in the common area doing what they want unrestricted. How restrictive and how long this training will be will definitely vary depending on breed of dog and the animals you are socialising with..
I find the labradors and retrievers are excellent for this type of training. They have a gentle nature and tend to "mother" the creatures they come across rather than herd or chase. My rescue retriever was excellent mates with my sebrights - they'd follow her around all day long and during the evenings she'd lie there and periodically swish her tail for them to pounce on.