Before you offer up your evenings and weekends, be sure that you are clear on what they need from you for this position. Typically the hours are laid out in the job description, but if it only says "part-time" or "full-time" and you are asked about the hours you're available to work, you may want to respond first with, "What hours do you need me to work?" Once they have laid out the expectations, you can tell them, "That sounds great! I'm available on those days and I can offer my weekends if I am needed as well." You want to show them that you're excited about the job and that you are willing to make yourself available to work when they need you.