Hi Abigail,
Your best bet would be to phone the council office in Castle Douglas as the have the records for the cemeteries in that area. If you have luck in locating the graves, let me know if any are in Dalbeattie cemetery and I can look them up and take photos for you next time I'm there. I do have the number somewhere but not to hand, and the name of the lady you need to speak to. Not much use am I, but wanted to respond to your message.
Lisa