I have friends who are 26. My sister, who is 33, is going back to school for a job in the medical field. By the time she graduates, she'll be almost 36 or 36 already. Don't sweat it. Also, don't be afraid to respectfully speak up and say that a degree is worth the time and energy. My mom's going back to school to do a social work degree, and that takes four years. As a full-time jobholder, who knows when she'll graduate? She knows, however, the importance of what she is doing.
It might also help to sit down with them and ask if they have any concerns specifically about your being in school at this point. They may be worried and not be expressing that. Nevertheless, talking to them about the issue would help a great deal. Just know we're behind you 100%.
Helen