I think you should talk to him more to find out what he is expecting and if you are comfortable with your skills to produce what he wants. Perhaps show him some of your work and ask him to bring you pictures of what he is thinking. Since the fabric is his grandmother's dresses, they may have a lot of meaning to him and the last thing you would want is to have him unhappy with the quilt after you cut them up. Whatever you do be very clear about what you can and can't do. As for price, there is another thread on this site in the last couple of days about what to charge, so flip back a couple of days and review all those comments.. I have never made a quilt for pay so can't be much help, sorry.