A bit more info might help with the search...have you found them on the census? Where were either of them born?
Having had a quick look at the indexes , no Sarah Jane Macken marries a Crawley and no Sarah Jane Crawley is born to a mother with MS Macken. So there could be a misspelled name here or some dissembling.
Also what is your source for Sarah jnr's death - there is no entry on FreeBMd for a death in 1911
I have found Robert and Sarah j snr on the census and whilst one census says both born Scotland, most have Robert born in Liverpool and Sarah in Dundalk, Irleand. It may be that Sarah jnr was also born in Ireland.
However, I cannot find young Sarah on any census at all - where was she after the marriage? Or have I got the wrong Robert and Sarah?