There are lots of outdoor activities at Gleneagles, just 15 mins up the road: golf, spa, falconry, clay pigeon shooting, and great bars and restaurants - including The American Bar!
The local gin distillery does great tastings, located in the shadow of Stirling Castle. There are great stories behind the names of the gins, and it's worth a couple of hours. Just remember to take a taxi!
Edinburgh is a must see city. The castle is worth a visit, as is the Old Town area. Take a tour and maybe an evening ghost tour - I'd recommend the "Real Mary King's Close" to go under the city and back to olde Edinburgh. And walk around George Street and St James Quarter if you have 'the shoppies'.
No trip to Scotland is complete without an encounter to feed the famous Highland Coos. Take some carrots and apples, or buy some from the shop. And you can pick up some souvenirs of your trip to the Highlands while you're there.
For the golfers, extend your visit and try your hand at the home of golf. St Andrews is 75 minutes drive from Cromlix, but worth the effort. Enter the ballot to play the famous Old Course - and even if you're not lucky enough to get a playing spot, there are 6 other courses to play in St Andrews.