I just contemplated the exact same thing. However, our attorney urged us to go through with the adoption. In any case, to help you with your question:
I live in Oklahoma, first of all. I know here, to change his name without the biological father's consent there must be an ad in a newspaper stating the desire to change his name, date of birth, your name, and some other details. The ad must run for I think it is 4 weeks. At which time, if no one responds to object you may complete the name change. The same procedure is used for the adoption.
Good Luck and if I can help, don't hesitate to hollar!
Amy
michaels_mom@cox.net