April Fool's gender reveal (with no reveal) targeted at elementary age cousins

So my husband and I want it to be a surprise, but the extended family (mostly the baby's cousins) wants a gender reveal. We are doing the baby shower in April, we thought about telling people it will be a shower/reveal on the 1st and have pink and blue reveal cupcakes with both genders and have a got you sign for the 5-9 year olds that have been founding us for the gender.

They are super into prank wars but there will be innocent bystanders who can't keep a secret who will be tricked into expecting a reveal. I'm due at the end of April