I have a 3.9 in my science prereqs. But with that being said, I repeated Chemistry. I was actually an SBU student for undergrad and took Chem there and didn't do so well in that class. After I graudated, I completed my Science prereqs. (along w/ chem) at a CUNY. My undergrad GPA was a 3.0. I didn't have any recent volunteer experience. Though it's been quite a view years since I've volunteered, I made sure I spoke about my experience in my personal statement like it was yesterday. It's not a requirement but it is recommended. I was in your situtation; working full-time didn't allow me to volunteer but, recent volunteer work will enchance your application.
At their information session, they explained that your personal statement is the most important part of your application. So I would advise you to give that your all so that they can get a feel for the kind of individual you are.