First, make sure you drag it out as a long as possible. Decide you can't tell them today, because the surgery is too far away. Or you can't tell them next week, because it's Christmas. In January, definitely don't tell them before E's seventh birthday. Then, when you've just about mustered up the courage to have the conversation, make sure to take your mother-in-law's advice to wait longer so that they won't get too stressed out too soon. Sounds good to you, yes? Because this is a conversation that is not going to be fun. Especially because your older son tends to get anxious. And he knows that your mom died of ovarian cancer. And they both know that George Harrison died of brain cancer because your husband felt it was a good idea to share this with them about two years ago, when they were five and three.
So, to avoid the dreaded "C" word, tell them it's a boo boo, which the folks at Mass General will tell you is a bad idea because your children will think their future boo boos mean surgery and hospitalization. So change your plan to include the " C" word. Then make sure to pick an evening when they are really worked up. Because that's always ideal for a serious conversation.
Make everyone sit at the table and say "I have something important to tell you."
Look them in the eyes and say, "Remember when I had that boo boo on my booby a little while ago (post-biopsy)? Well, turns out that was breast cancer. But it's going to be OK because it was caught really really early. And it's not like my mother's cancer, which was down here (point to area) and caught very late. So the doctors can fix it."
Wait. Look for signs of tears. Or anxiety. Ask "Do you have any questions?"
Respond to the silence that follows by adding what is likely too much information by saying, "So what they are going to do is remove this boob, and replace it with a new boob."
Make sure your husband, or significant other, then says, "A bionic boob!"
Watch your children cry from laughing so hard.
Tolerate the onslaught of questions that follows for approximately the next ten minutes:
"Mommy, will your bionic boob grow a butt?"
"Will it grow a little arm that can pick up legos?"
"Will it poop on your other boob?"
"Will it be able to do karate?"
"Will it grow a penis?"
And so on.
For a moment, feel a wee bit of sadness over this unexpected reaction. You are their mother, for Christ's sake. The little shits should be feeling much worse.
But let the negativity pass.
Truth is, you could not have hoped for a better response. Tell them that if they talk about your bionic boob at school, they will lose any video game privileges for a week. Then let 'em laugh.