Yes bananas are very safe for puppies to eat.
The bananas are soft enough for a new puppy of at least 4 weeks of age to eat but just don't feed the puppy too much bananas because it could lead to diarrhea in the puppy and stomach issues.
But cutting up a banana and sharing it among the puppies perfectly okay.
I used to share bananas with puppies when I had them and they loved them and it makes for a great healthy snack for the puppy.
But also feed the puppy some wet puppy food as well because they need more than just bananas and other foods.
Puppies and dogs can eat many other human foods as well such as apples, carrots, rice etc.