In MO, where I live the legal age of adulthood is 17. Some states it is 17, some 18. If I were you I would check into that. If legal age in your state is 17, I would just wait a few months and do an adult adoption. Then you would not need anyone's consent other than yours, your husband's and your (now adult) daughter. Then you could complete your adoption without stirring up a hornets nest, although if your daughter is interested in meeting her birthparents....this would be the perfect opportunity to make that happen.
Attorney adoption fees vary by state, experience, and time frame. It all really depends on which adoption attorney you choose. It can range from a few hundred dollars to a few thousand. There isn’t one set rate, so it is important to consider multiple adoption attorneys before you settle on one. Remember that you don’t have to work with the first adoption attorney you come across. Explore your options so that you can be confident and comfortable in your final decision.
When my wife and I adopted our son, we were told that we needed to hire multiple attorneys. One to represent the birth mother. One to represent the child. One to represent the birth father. And one to represent us. When we adopted our daughter we needed even more. One for the child. One for the birth mother. One for us. And one for each of the three possible birth fathers! We were outnumbered! Since no agency was involved, the attorney fees, the home study and the court costs were our only expenses. And when it came time to file our income taxes we claimed the adoption tax credit and were reimbursed the entire amount. Both times. We were fortunate. Adoptions can be, and in most cases are much more expensive.