Technically you can put them in at any time if the larger geese don't mind having them around. Usually I move mine in with the adults at around 6-8 weeks. Definitely keep an eye on them at first. If you have a gander or a motherly goose you trust, put that one in with the goslings at first. Once a single goose in a small group adopts/acecpts new geese, the others seem much more willing to go along with the idea. Plus it means you have at least one goose in the gaggle that will protect and teach the goslings.