I don't think that staying together for the sake of the dc is ever a good thing tbh. Regardless of what is right or wrong in the relationship. If you are not happy and have no inclination to fix things, then it would probably be better to leave.
Having said that, like others have said happy relationships take work and compromise. They don't just happen and even the most loving couple will have bad patches.
The question you should be asking is 'is there enough left for you to want to work at it?' If not, then yes, the dc would be happier if you were apart.