Coming from someone who had parents who were absolutely miserable in their marriage (and were often verbally abusive to each other and at some point, even physically...); I would have preferred they had gotten a divorced than stayed in it "because" of me. Which, they have at some point blamed on me.
I would hate, God forbid, that your children end up feeling the way I felt when I saw how miserable they were, which in turn made me miserable (But, I also suffered horrific abuse by the both of them).
Please, if you are unhappy and you've already tried to salvage it.. such as counseling, sitting down one-on-one to communicate the issues (if possible)... Do not stay in it and do not drag it out. You will give your children a much happier (and smoother) life if you get out of it sooner rather than later. Again, I only urge this option if you've already done EVERYTHING to fix it.
At some point, you have to realize when the 'risk' is worth the end. Also, if your kids are of age, and you're close enough with them, i'd even go to them personally. While it may seem awful to bring such a scary topic up, sometimes...they already see the misery and will often blame themselves for the misery. IF I were a parent (which I'm not), I definitely would not want my children to feel responsible for the 'shams' of the marriage.
I wish you the best of luck. Just remember, it can be more detrimental to stay in it than leave. Assess your situation, list out your options, and attack the best solution. :)