Telling my parents on Mother's Day

Is anyone else planning on announcing to family on Mother's Day? That will be 12 weeks for me.
What are your ideas?
My parent's first grandchild was born in February so I got my mom a "Best Grandma Ever" sign. I was going to give it to her and see if she figures out that I'm pregnant (baby #1, been TTC for 2 years), or just thinks it is referring to the 1st grandchild. I'm sure my face will give it away!