Deancey - I have done cert IV nursing. I was a single mum at the time i did it and my dd was only 3, i had alot of support from family but i managed it fine, it was difficult at times especially when on placements as the hours were usually early and being on my own it was hard dragging dd out of bed at 6am etc. I absolutely loved it though, and i think you will be fine, just need to be organised. It was 4 days a week for 12 months then and i worked 2 days so i was very busy. I am thinking of going back to more study also, just not sure if i want to continue on that path or go business.
Im sure you will be fine, and they are usually fairly helpful if it gets too much at sertain stages you maybe able to drop a subject and pick it up later on. I say go for it.