When did you tell your older child?

Rachael
Hi everyone. I'm 7w2d right now and my first kid is 5.5 years old. I'm not a high risk pregnancy and don't have a history of miscarriage. For other moms with children already, when did you tell them you were pregnant? I'm dying to let him know why his mama has been so sick and miserable and I know he's going to be so excited.