Life's far too short to spend it being disappointed and miserable with anyone that doesn't care for you. Children aren't stupid and most would rather Mum and Dad were apart but happy rather than feel responsible that Mum and Dad opted for a life of misery together 'for their sake'.
Even if you're not quite ready to split for good, make arrangements so that you spend a good month or two apart. If you find life is suddenly a lot better then you'll know you made the right choice. If you find you miss each other then you can choose a different path