Telling my step kids...

I need some advice. I'm almost 12 weeks and we have told most people close to us except my husband's 2 other kids. We unfortunately don't have much of a relationship with them due to issues with the mother. The kids are 17 and 14. I'm so worried they will be upset and resentful about dad having another kid. Do we just dive in and hope for the best? Do we slowly ease into it? I don't want to have to hide this from them. Not sure how to go about this.