My dog is bullied by geese (she did find that if she puts her back to their pen she can get a free goose bite "massage") even though she was not agressive towards them, and would protect them I still never let them freerange when she was out, she was penned when they were out of their yard. Even playing she could easily hurt or kill them unintentionally. Since your dogs seem to already have a strong prey instinct against fowl I would be even more worried. It would be better to get a dog kennel for the dog when the geese are out, or crate him, if hes just locked in the house and the type of dog to barge out soon as he hears the door open. The other thing ould be to extend the goose pen or set up a fenced area for them so they are seperated at all times. You can sometimes find used kennels or fencing cheap on craigslist and it would save a lot of heartbreak.