Has anyone done it? Are there any tips you can give me?

My sister & new BIL are coming home from their honeymoon this weekend so we're having a BBQ & I'm baking a cake. They are both caramel obsessed, so I'm making a caramel mud cake & I want to do caramel ganache on it. I have white chocolate & caramel chocolate oil, but I'm not sure how much to use or if it will even work in white chocolate! Any ideas?