A couple of people have posted on here looking for trails around Aviemore
This is nothing to do with trails but I was at Glenmore Lodge earlier this week and found you can have a day on their skills track (no bike or tuition included) and a main course with glass of wine for £10. I know nothing about the bike facilities as I was on a kayaking course but what I did see was excellent. The food was pretty good and in epic quantities aimed at people who’ve been kayaking/hill walking/biking all day.
Mon-Thur only and details here