I'm aware of the process and that it's not compulsory etc... Just want to know, do I have to give the embassy one of the 2 pretty coloured certificates or is 1 of the copies of the more detailed stamped documents that they give you at the 'ceremony' at the Amphur and we have used for changing her id and housebook etc enough?

Best contact the embassy. I would think you would (also) need the more detailed documents, as they give more details.