Hi B.,
I am a work-at-home mom, and I am in the same boat. I try to work as much as I can when my son is napping or asleep, but it's impossible to get it all done during those times.
My son just turned two. When he was younger I had the living room gated off. Now he has the run of the house. I am lucky that I work off a laptop. What I do is set my laptop up in the dining room, which is connected to the living room, which is where the majority of his toys are. I like this because I can work and keep an eye on him. It's the best situation.
He does often wander into the family room, though, where the TV is. He knows how to turn it on and off himself and sometimes will watch a half hour's worth of TV before returning to his toys. When that happens I check on him often. He is usually just laying on the floor in front of the TV.
However, I try to only do my work when he is keeping himself busy. If he needs my attention, which is often, he comes over and grabs me by the finger and pulls. That's it for the computer. I give him the attention he needs and then work again when I can. Sometimes he only wants a minute of attention, like he wants to be sure I'm still there for him. A big hug and kiss and he's off again. Sometimes he wants me to sit and play with him a long while. I make him my priority. This gets stressful when I have a deadline, but I do my best.
I must say that, contrary to popular belief, it's not ideal to work from home. It is very difficult. Neither your work nor your children get your full attention all the time. It's impossible. It's a constant juggling act.
I do recommend moving your work, if possible, to a more neutral place where you can keep an eye on him while he's keeping himself busy. Maybe get a laptop or move the computer. My son has fallen a couple of times, and I was right there to comfort him. It's impossible to work and watch him 24/7, but at least you can glance up and see what he's up to.
I think it's great that you're taking the course. Good luck to you!!