Update....I'm pretty sure I have 2 females. We've been taking the eggs out of the nest and every morning there are 2, 1 in the nest and 1 by their pool. I've read that some ducks do lay more than 1 egg a day but it's not very likely and it would explain why we have so many eggs. Would it be safe to get a drake or would we need more females than just 2?
It would be preferable to have at least 3 ducks with your drake, but some people keep breeders in trios (2 ducks and a drake) without any problems.