Yes we do. The Concise Scots Dictionary and the English-Scots Dictionary provide guidance in these matters. Every language looks to its dictionaries to authorise its forms and we should do the same. It has a history and a literature behind it and its forms have an etymology. Slang is universal and subject to fashion.
Language is local and evolving.
When teaching Scots, one of your first tasks will be to show children the difference between Scots and slang. A. Start with how they speak, then try to write it down as it sounds, consulting a dictionary for help with spelling consistency. There are also local writers, like Sheena Blackhall, Liz Niven, Rhoda Bulter, Bill Rae, David Ogston, Ellie McDonald, Willie Neill and many others. There is nothing against using spoken Scots in literature as the old divisions between spoken and literary language have largely disappeared in the modern world, where radio, television,film and video play as important a part as books in our lives. This can be done by pointing to the fact that we have three languages at our disposal in Scotland, which means that the children will have access to three cultures, instead of only one.