In my eyes, the main reason you would come to Seefeld would be to enjoy the variety of outdoor activities. The scenery is breathtaking and the surrounding mountains provide amazing views in every direction. Toss in mountain lakes, flower-filled meadows, amazing trails, and the charming Austrian villages, and you have a winning formula for everyone.
There is something for all fitness levels, and you can go as extreme as you want (and a little bit beyond). Readily available activities include mountain biking (and road biking), hiking, canyoning/rock climbing, white water rafting, paragliding, golf, tennis, and almost anything else you can do outside. You would have to spend months to try all of the mountain trails available . . . and it might take months to fully adjust to the elevation because you definitely feel the effects as you exercise. But that just makes it that much more satisfying when you finish a great ride or hike.
You can easily find a mountain guide at any of the local sports shops. Even if the shop doesn’t offer the activity, you can bet they will be able to recommend and call somebody for you. There are also dozens of outdoor tour companies. I particularly enjoyed the white water rafting tour (it was my first white water rafting excursion, and was quite a thrill). But a guide for most things isn’t necessary. There are plenty of trail maps and everything is nicely marked so that you can hit the trails on your own.