The answer depends on your personal attributes and your academic abilities. If you are very dedicated, very disciplined, smart, and willing to sacrifice most or all of your spare time for the next four years then yes, you can probably do it.
I went to law school at a part time evening program while juggling a family, a mortgage, and other responsibilities. It is a grueling process, period. Law school is far more demanding than undergrad, the two are not even remotely comparable. You will be expected to read hundreds of pages of dense, often boring material every week and to be able to utilize what you've learned in a unique way. The amount of preparation that would have landed you an "A" in undergrad will get you a C- in law school.
More than anything else you have to be absolutely committed to becoming a lawyer, you have to want it badly. I was very committed and had a very supportive spouse (also a lawyer), and it was still a grind. There were many times when I felt like packing it in. Law school significantly reduced the amount of time I had with my family, and wore me out mentally. I think that the idea of "part time" law school is a misnomer, because you are actually forced to adopt a seven-day work week. When you're not in class or at your job you will be studying, briefing, or researching.
You need to ask yourself if you want to be a lawyer badly enough to give up time with your son, and to forego any real down time for the next four years.
If you go to an online school you'll have to set aside additional time to prepare for the FYLSE ("baby bar"), as well as the MPRE (all law students). After law school, of course, you'll need to set aside two or three months to prepare for the bar exam. It would be very difficult to work and prepare for the bar simultaneously. Bar prep is a fulltime job.
Now for the good news. If you successful in this endeavor you get to be a lawyer, and there can be a great deal of personal and professional satisfaction in that. This might sound corny, but when people find out you're a lawyer they often treat you with respect, listen more closely to your opinions, and are deferential. It's kind of a nice little ego boost that helps those fatigue-ridden years seem worthwhile.
Lastly, you mentioned online school. I assume you know that there are significant restrictions imposed on online grads. I don't know where you are located, but the vast majority of states will not let you sit for the bar. Additionally, you'll be on your own as far as finding internships and jobs, and many employers will be wary of your degree. If there is any way you can attend an ABA or CBE accredited school, seriously consider that option.
Hope this helped, and I wish you the best of luck!