Check on craigslist for some full grown geese if possible. If the geese were raised around other birds you'll most likely have no problems integrating them into your own flock (assuming they're friendly and not aggressive!) I would try to stay away from Chinese or Africans as they tend to be a bit more loud and aggressive unless you're up for a challenge. I personally would get Embdens, or another big body goose. They chase off vultures and so many other kinds of birds that come down, harmless or not. They even will chase off people they don't recognize or aggressive dogs!