Some sites say you can have 3-5 geese per gander depending on the breed. However, the problem you can come into having so many geese is if the gander chooses a mate. A friend had this problem this past spring. She had a pair of pilgrims who were 2 years old then she had 2 yearling geese she kept from the pair's eggs last year. All 3 girls started laying, but only the 2-year-old's eggs were fertile. The gander paid no attention whatsoever to the 2 younger geese.
I have 11 geese for next year, 10 embdens and 1 chinese (oops!). As far as my sexing is concerned, I have 5 embden pairs. The chinese 'should' be a female, but I'll have to wait and see. If it's not a girl it will be finding a new home...might be anyway, haven't decided yet for sure.