Anyone with older kids who didn't want another sibling?

I have 3 girls, 13, 11, and 3. My 13 yr old is always saying she doesn't want us to have another one. Now I got a BFP and I'm not sure how to tell them. I won't tell them anything till I'm at least 12 weeks but it makes me anxious. I was thinking of getting my 3 ur old a shirt that says "I'm going to be a big sister" that's sort of how I told them about her in 2010.