First, Congratulations on Law School!
Second, I have been a single parent and attended college and I am currently married and working full time while still attending school. From my experience you have more time when you are a single parent. It's only you and your son and not a husband and wifely duties to attend to. (Don't get the wrong idea; I love my family and duties very much) My husband does help out and is supportive with kids and housework and even cooking, but that is still an added responsibility. I am trying to say I think you are at more of an advantage if you do it now especially if you plan on expanding your family later.
Like some of the other responses, if you wait there is all of that lost time to consider. However, if you go you need to create a time management plan that leaves room for the unexpected. I went from three classes in the beginning to one class currently and I take that class online since attending campus would be too difficult right now. True, it does take longer, but I still have plenty of time for spending with my kids and instructing.
Can you lighten your load? Take one or two classes, out of those take one online. I would not suggest quitting your current job due to the economic situation, but of course you would have to decide that. Homework is very time consuming for my one class and my other duties so evaluate your homework in all your classes. Would it be time consuming the majority of the little extra time you have left? So now not only are you gone to work, then school but when you come home you have tons of homework and study time.
Depending on what you decide, a little tip that I have is scheduling homework time with my son. We both sit and do our homework together, and he enjoys this and it leads to open conversation.
With that said, you sound like a very good mom. Unless you are confident in the morals of friends and family then think twice about who will be assisting you. Your son will be learning and molded based on their values and morals since he will be with them for the majority of the time you attend school. I had to think about this myself and that's why I lightened my load and decided to devote the majority of my time to my kids.
If you are a spiritual person, pray on it. Speak with a counselor and explain everything. Create what a schedule would look like if you added this much schooling. Create a schedule if you only took a couple of classes. Don't forget to add homework and study time. Definitely leave space for the unexpected (anything out of the ordinary, sick child, etc.)then and decide from their.