I am sorry that you are going through this. It is the toughest, hardest thing, but it is better then letting sweet Bo suffer. We put our Kingy down last September and I just knew that it was "time" and although it hurt so bad, I knew he was in better place. Our daughter was 6 at the time. She knew King was sick, but we took her on to school that day and had the vet come to the house.Thjat was alot more peaceful for everyone, especially him. She asked me if today was the day Kingy was going to die. I told her I hoped not for our sake, but he would be happier if he were in heaven.
I will say prayers for you because it hurts. We all know this, but it is a small thing we can do for our babies after they have been such great kids.
My daughter handled his death okay at first, but that night she broke down, along with myself and my husband we all just held each other and cried and cried. She did good after a week, but as far as my husband and I go, we still cry if we talk about him or think about him.
We got a new baby Boxer just a month after King died after swearing we would never have another animal again because it hurts too darn bad, but it helped all of us. And now as I speak I have a huge 7 month old "son" chasing the cat, chewing my daughters toys and just enriching our lives as sweet King did for 10 years. Hang in there. I would not recommend a small child being there, they just can't wrap their brains around the magnitude and the finality of it all. I have a hard time myself. Best wishes, you'll know when it is time.