As a guy, I reinforce what Airto said--

If you have not talked with your husband about this, and if he is not expecting it, then you are about to create a nightmare, not just for yourself, not just for him, but for the five kids--

Don't say that he "knows" that you are unhappy--guys can drink heavily, cheat on their wives, abandon them, and even beat them, and still be completely surprised when their wives leave, file for divorce, or even file for a restraining order--we are kind of dumb that way--

We are also creatures of habit, and it is hard to tell(even for us) how we will respond to anything that shakes up our daily routine(no matter how empty or unpleasant it may seem)--your best shot, generally, is to lay a solid foundation for what is going to happen, before you drop any bombs--otherwise, we scramble in a panic to find bombs of our own to drop--

Lawyers should be the last resort, for negotiating child custody, property, and financial arrangements, when other options have failed--If you don't know what your options are, a family therapist, a counselor, a clergy person, or some sort of women's support group should be your first stop.

I am not suggesting that you you give things one more try, or anything like that--if, after 25 years and five kids, you want to bail, you probably have plenty of good reasons--I am just saying that you shouldn't make any sudden moves--remember, no matter how bad things seem, the can always get worse--

If you, or your kids, are in fear of your lives, it is a slightly different story--go to one of the above, and tell them what is going on, so they can get you into a protected situation, ASAP--even in this case, the lawyers come into the picture later--