So mother bunny thought making a den near your house was a safe place. Obviously she sniffed around and smelled no predators in that area. Obviously you take your dog in at night. Obviously she planned to spend many happy nights with her babies eating the green grass near your house. But she was wrong.

You watched the babies die and now you and wife feel guilty.

Life is a learning experience. Next time your wife will know exactly when to kick you out that back door to rescue bunnies. End of story.