Make Up A Kid Day!
Get a custom-made mug with a picture of a baby all over it and caption the photo with the declaration: "I Wish I Loved Him But I Don't." When a coworker raises his eyebrow at the mug while you're getting a coffee fillup in the break room, say, "Yeah. That's my son Joey."
Your coworker won't know what to say and will try to leave. Block the doorway.
"Everything else in my life feels so right. My job. My marriage to my husband. My parents are my best friends in the world."
"But my son, when I hold him, I feel...unmoved. It feels like we're remaining mother and son out of duty." Sip your coffee. "Sometimes I wonder if I only had him out of a sense of fashion."
Then slip out of the breakroom without a goodbye, go to your department manager and tell him you accept his offer to go perm.
Happy Make Up A Kid Day!