A lot of the damage done to children by divorce is to do with how their parents handled the whole thing, not in the mere fact that their parents don't live together. Sometimes a split is a positive thing, and not always when one parent is abusive; if they just don't get on it can ruin the atmosphere too. However, if they use the children as sticks to beat each other with, the damage can be dreadful.
Children don't always get what they want, especially when it's not good for them - and I'd argue that the example of one parent doing everything while the other slobs around is not at all a good one. Will your daughters grow up to accept they have to do everything, and that once they have children that's it, they're stuck? Will your sons grow up to believe that all that household stuff is a woman's job, and as long as they don't knock her around they're doing enough? Is this an example they ought to have? For that matter, will you have more energy to spend on them when there isn't an extra drag in the form of a grown-up child?
What kind of a father is he - engaged, hands-on, helping with homework, taking them out at weekends, or just being vaguely nice while you do all that stuff as well? I would argue this is a factor not in whether you should necessarily stay together, but in the residence/access arrangements. A good father will be a good co-parent and you will even learn to appreciate the free time when the kids are with him! If he's nice but a bit useless, as with pretty much everything else, having more limited access may actually encourage him to step up and make the most of the time he does have with them.
And finally: giving yourself permission to leave, and knowing you can and will put it into action, may - just may - give Mr Nice-But-Useless a proper kick up the ass so he finally realises he has to pull his weight. Like an alcoholic, realising he stands to lose everything might be the rock bottom from which he turns it all around. This is by no means guaranteed or even likely, but one thing that is certain is that if you don't change anything, nothing will change. There isn't a magic form of words that will suddenly make someone mend their ways if it isn't in their interests to do so, sadly. If there were you'd have found it by now.