Yes, 7-12mg is a perfectly reasonable, very conservative amount. 12mg of caffeine is about equal to the amount of caffeine in a liquid ounce of 'average' coffee. (Source USDA)
Take care not to pack the scoop. Pure caffeine is a potentially dangerous ingredient. Microscoops vary even more than what is implied by your question, I've seen them as large as 50mg; a comment here tells of a 100mg microscoop. Again, take care, and know exactly what you have.
For greater accuracy, consider a milligram scale which can be had for about $20 US.