Geese nesting house - A-frame - predator proof????

Thinking way ahead here ;-)
We got some ducks and geese this year and I am in love with them! We have them fenced in in our newly planted orchard with a coop for the night that they share. We lock them up every night since we have lots of raccoons and opossums. Once it gets dark they all go in the coop on their own. Come next spring I would like the geese to raise some babies. We have 2 pair of American Buff. Since I don't want them to take over the coop as their nesting space I thought about putting up 2 A-frame duck nests like I have seen here on this site and mentioned in Holderreads "Book of Geese". My question now is how to make them predator proof ……
If I just make a swinging door in the front that I lock up at night will they let me do that or put up a fight if I come close to the nest. And if I do that I would have to make it pretty big to accommodate the little goslings as well. How long will they use the nest after hatching? When will they start using the coop again after the little ones hatched??
Any better idea of making a predator proof nesting area for the geese??

Thanks,