Porters or Crawfords

David & Mattie?s marriage appears to have been prior to the start of statutory registration of non RC marriages (April 1845). Certainly there is no record of it after that date. Unless it was an RC ceremony, it must have taken place prior to April 1845. Birth registration didn?t start till 1864 so you won?t find birth certificates for the children. You might find their baptisms though.

You will need to rely on church records, where they still exist. To do that ideally you need to know the couples denomination(s) and have some idea of where the family came from in Donegal. Do have any information about that? (Looking at the 1901 census for the county there are 433 people named Porter, of all denominations. There are 331 Crawfords, again of all denominations).

There?s no sign of the marriage or of any children to a couple with those surnames on the rootsireland site, so that suggests that either the records you need are not on-line or that they don?t exists. (Not all churches have records for the years you need).