You sound similar to me. I was a dental assistant for 15 years then decided to go back to school and try for a DDS. I already had my BA from 15 years earlier, but I had to take/retake all the prerequisites (except physics) since everything was so old. I took some of my classes at a community college (GC 1 & 2, Bio, Micro, Anatomy) I was told by the admissions board that I needed to take OChem 1 & 2 and Biochem at a university. Looking back it would have been better to take Micro and Anatomy at a university too even though even though I don't recall if they were a prereq or not. It took 4 tries at the DAT and 3 application cycles before I got in. Truth is it's harder to get good grade the older you get. I have to study 3 times as much only to do half as well as students in their 20's. I'm a DS2 and love every minute of it. Since I'm very non-traditional I know I won't be living in a mansion or driving a Porsche. I'll have to work hard to get my debts paid off before I retire. People who don't know me think I'm crazy for going back to school. But friends and family think it's great I did.
I personally would not take any classes online. From talking to different admissions boards, some weren't very happy about the community college route and I'm sure they would be less happy about online. I know a university is more expensive but you'll have better odds of getting accepted. One plus you have is the dental experience. I didn't have anyone question my desire to be in the dental field. They knew that I knew what was expected of me and what to expect in school.
Good Luck