While Scotland was fighting the English for independence, it was also fighting among itself. Similar to Japanese Shoguns, Scottish clans vied for supremacy. Alexander Stewart attempted to take on a numerically superior force. He was confident in his heavily armed knights and men-at-arms.

Scottish Crown and Duke of Albany
Alexander Stewart, Earl of Mar
3,000 Infantry and Heavy Knights

Lordship of the Isles
Donald Islay, Lord of the Isles
10,000 Infantry, mostly peasant militia

Wargame
Use DBA or DBM or similar rulesets.
2 Players

Instead of points, the Lordship of the Isles should have 3x the number of stands as the Scottish Crown. The Scottish crown should have heavy armor and elite knights and infantry, roughly 50% of each, with no archers.

The Lordship of the Isles should have warbands, peasants, and some psioli, such as peasant archers. They could also have a small number of spearmen.

Set the table as you wish; traditionally, the battle took place over open ground in the Scottish highlands, where there would be shrubbery and rocky outcroppings.

The objective for either side is to win the day. This is a simple battle of elite vs. numerical superiority. I did not try to balance the battle based on points.