Take a deep breathe and try to relax. Is this a new situation with her? Has she talked about divorce before?
This sounds like something you can work on together. Can you turn toward her and figure out together how to address her unhappiness? Can you figure out together how to bring joy and passion into your lives?
These years with very small children are very tough. It sounds like your wife is depressed and needing some professional help. Can you help her get that?
I think it is time to roll up your sleeves and see how you can work to make this marriage awesome. I wouldn''t give up on it so quickly.