Geese sleep on the ground. If they’re going to be with the flock during the day, I don’t think they need a huge shelter. Smaller is cozier as long as it’s not TOO small. (And unless they’ll be confined all winter, more or less.) I’ve been reading Dave Holderread’s “The Book of Geese.” You can get it from Meyer Hatchery or from his own website, and I’m very glad I bought it.
I’ll be getting a gander and three geese in May, American Buff. As you may have read, they’re mid-sized and reputedly gentle and calm. Hopefully this will bear out, but if not, there’s always the roasting pan.

Good luck to us both, and do get the book. You won’t regret it.