Margie, that is a beautiful sentiment. ♥
Sarah, as Margie said, please don't be hard on yourself with the "what ifs". We all do that at these difficult times, and it's really not good for you. I realize that Missy's passing was very, very sudden, which can be a blessing at least for Missy, not so much for you.
Most of us have been where you are right now, and will be again. It's never easy. Some people simply don't understand what it is to lose a beloved dog, but everyone here does. We know that Missy was your heart. People who aren't "dog people" often wonder why a week later we aren't back to our old selves. They simply don't understand the deep bond and connection we have with our four legged family members.
Like you, I also have children. At the time I lost my beloved Emma (my Golden) my youngest son was having his 2nd Birthday, and it was Easter Weekend. My older son was 6 and a half, and was devastated as Emma was there when he was born. This is also a time when we have to think about our children and what lessons we'll teach them about love and loss. It's a tall order.
Everyone here understands, and when you need to talk about it or just share, we'll listen and hopefully offer some comfort. I sometimes think it's almost harder than losing a human loved one as the rest of the world understands that pain, but they don't necessarily when it comes to our dogs.
You do have my most profound sympathies.