McKinlay is a sept of the Farquharson clan and thus could use their crest.
Have a look at the website http://www.farquharson-clan.co.uk/
The clan system was almostly completely destroyed by the English after the failure 1745 Jacobite Rebellion and the defeat of Bonnie Prince Charlie at Culloden. The wearing of tartan was banned by law until 1782 and Scotland was controlled by a English Redcoat army who constructed many miles of roads to keep the country under control. The various laws made it almost impossible for the system to continue.
Our present concept of Scottishness was created by Sir Walter Scott, when he was asked to stage manage the visit of the new king George IV to Edinburgh in 1821. In 3 weeks he organised an event which included providing a complete Tartan outfit for the king. Since tartan had been outlawed this required creating not only a tartan for the king but also tartans for the Highland chiefs. Some people consider that the whole Scottish Tartan History really dates from Scott's creations for the kings visit.
In addition at that time Scotland was changing from a mainly rural society, in which the clan system could thrive, to an industrial urban one where the old clan concepts no longer applied.
The clan system today in Scotland is more of a social scene where those interested get together for organised events rather than anything of the old "family" structure.
If you want to find more information put the key words into Google. It is amazing what you can find and how well informed you can appear.
I hope this helps.