I've trained my son's Golden faster than any of my dogs! He's so good with chickens. Even my daughter's Corgi is good with them. My cat's can't be trusted around baby chickens but I've seen my hens gang up and charge my poor feral kitty! No worries there!
It's a great idea to keep him on leash for a while, for introductions. Make him sit, stay and watch the chickens. Like you've noticed already It's not necessarily chickens scratching and foraging that makes prey drive kick in, it's chickens running (which is hilarious to us humans, but signals...