Telling your children

Those of you who have children already when did you or when will you plan on telling your kids? I have two kids (3 & 5) and want to tell them sooo bad but once my daughter (5 year old) knows she will tell EVERYONE! lol I didn't have to worry about this when I was preggo with my son bc my daughter was only 14 months old! Any cute ideas for telling your kids as well (keeping in mind they are young)? 😊