I got Africans for the same reason. This has been my experience.
We have a lot of free range area and a lot of poultry. One of our African Ganders was booted out of the gaggle early on and he spends all his time with the ducks, which I like a lot. However the ducks don't all stay together as we have enough of them that they break up into smaller flocks. This appears to drive the gander nuts because he can't keep them all together. From my point of view it's okay because there's always some geese somewhere and though they like to wander further than the ducks do, most of the time there are geese around the ducks.
When it comes to chickens though, it's a different thing. They range in much smaller groups and don't seem too interested in geese and the geese don't seem to be interested in them. They rarely flock together. However if the geese give out an aerial alarm call, no matter where the geese are in relation to the chickens, the chickens run and hide. They learned the hard way by getting picked off one by one for a few days when they were younger to a pair of cooper's hawks. That said, the chickens tend to like to head out to the understory where they are vulnerable to brush predators, like the cooper's hawk, which the geese never see. So the geese do help them when they are in the open and everyone is at risk to the same overhead predators (large circling raptors), but the geese are not helpful to the chickens when the chickens go into the understory.
And yes, get at least two geese. Also know that their behavior is different during the breeding season than during the rest of the year or you won't be happy with these wonderful creatures.
