Can I call child protective services on my neighbor discreetly?

I have a concern. I live in an apartment with my neighbor who lives below me and she is a young mother who has two children, two girls around the ages of 1 and 5 years old. I notice that on a daily basis she is always yelling and screaming at the top of her lungs at them, she tells the baby to shut up or shut the f*** up and all they do is cry. I feel soo sorry for them and I try not to get myself involved in their business but im really concerned that those kids are emotionally abused. There was one particular day about a year ago that I came home from work and I heard her arguing with the childrens father and she threatened to stab him if he didn't leave her apartment (they don't live together, thank god!) Everytime though that they are together they are arguing in front of the children and she uses profanity all the time and thats just not right. I want to contact children protective services on her but Im concerned that she will find out that it was me who called and then that in turn will get me in trouble with her, which I don't want to have any trouble with her but my concern is for those children. If I called C.P.S. on her would she find out it was me? Would I have to go any further than making a report about her? Any help or advice would be appreciated! I live in Ontario by the way.