I think it's worth making the drive -- if not every week, say once a month? On-line groups like this one are helpful, but a formal "12-step meeting" is different. There's the meeting itself, chatting with people afterwards, and maybe even a "meeting after the meeting," which my local group does at a coffee shop. It's really valuable to see people in person and share with them in a structured setting.
The workbook is great -- but I don't recommend trying to do it by yourself. It's pretty intense, and I think it's better to find a sponsor and sit down with him/her to talk about each section of the book. If you can't get an ACOA sponsor nearby, find someone in Al-Anon who is an adult-child (that would be most of them!), and might be willing/able to work with you.
T