I understand/applaud your wanting to do therapy before the marriage break-up decision is made but I don't know that it can work if you don't think it will. My husband's ex-wife wanted therapy and I suggested he go and he did but he wasn't committed to it working so it didn't for him.

I would do as kimmydawn suggests and go yourself now and see where you head is actually at. No way you can determine when will be good/bad for you to split for your son or his mother, that's wholly up to their own personalities/life experiences and characters.