Life is a gift that has been given to us, and while it is ours, and we can do what we want with it; it really is a gift that is best used by giving it to others.
So, instead of taking your life; make the decision to live it for others, for you kids, and then your grandkids.
You are obviously still in the raising your kids stage, and even at the teenage time where they ignore you. However that is just a stage, they do come back, and the relationship you have with your adult kids is wonderful.
And then the grandkids. You said that your kids are your world; just wait until you have grandkids. Itis amazing. You get to see, all over again, the things that make you smile, laugh and cry as they learn, discover and grow.
I know that for you life is hard, and you want out, but before taking that step; don't just ask if your kids will be ok, ask what enriching of their lives, and the lives of their children will be missed by your death.
So, instead of taking your life, make the determination to invest it into the lives of others.