1010 vertical meters, kid area, nice offpiste in the woods, close to Oslo
Not too much open offpiste terrain
Norefjell is a nice place to ski approximately 1,5 hours drive from Oslo. You have nice hotels with kid friendly area just outside, and nice slopes for beginners to experts. A good place to stay is Norefjell Spa Resort and a good place to eat is Norefjellhytta. Both are quite expensive but you get what you pay for.