I find the secret to non-aggressive geese is to get them young, develop a routine and have a regular amount of human contact. (A bit like babies really)
If you can provide a heat lamp you can get them as day old chicks. Otherwise, you can get them at two weeks old, off heat. We keep them in a shed with lots of straw. I wouldn't confine them with chickens but they free range together quite happily if there is room for them all to keep a respectful distance.
Ours follow us everywhere if we have a scoop of whole wheat in our hand which is only morning and evening. The rest of the time they are eating all the grass

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if you have a breeding group the gander can be aggressive if he is defending a nest. Perhaps the answer is to raise a dozen or so for Christmas? They will keep the grass down when it is growing during the summer but won't grow old enough to breed.