Been skiing here for 30 years plus. Children first put on skis in Altenmarkt aged 3 and 4. They are still flat out in their mid 20's. Happy Ski School fantastic!
The only downside to this location is that if you want to really explore you need a car. Never a problem for us because we drove to Austria or hired a car at airport. Pistes are well groomed and the lifts are superb for a small mountain. However, you can a bus to the head of the Valley and go to Zauchense ( Michael Walchofer's home resort) which is a big resort and linked to Flauchauwinkl and Kleinarl. Next year they are opening a link from Kleinarl to the top of the G Link in Flachau. (Should have done this years ago). This will allow you to ski from Zauchense to the far end of Wagrain all linked!
The town is lovely and traditional Austrian. It's a busy working town the Atomic factory is here as well! Radstadt is a traditional Austrian walled town and also stunning. Lots of history.
If you want the traditional Austrian experience, sleigh rides in the forest etc and a quiet family atmosphere it's difficult to beat. I'm going back there in a few weeks with my wife and parents who still ski in their 70's. From there we have ski'd Obertauern, Schladming, Reiteralm, Flachau, Wagrain and even up to the Gastein's.
For family I would definitely recommend and if you don't mind driving you have access to top class resorts covered on your ski pass within 20 mins tops once all the lessons phases have finished!