How to tell your other children?

Brandy <3 • I am 28 years old. My husband and I currently have two children. Both boys, ages 12 and 6. Hoping for this little one growing to be a girl ;)
So I've come up with a way to tell my husband that we are expecting baby number 3 but I want to do something different than just a big bro shirt for our 2 other boys. Anyone know of any good ideas they have heard or tried when sharing the good news with their other children? Btw our boys are ages 12 and 6. Thanks in advance :)