Take your speedos, it’s nice swimming in the lake and the lido there is ok too. Check out if the Red Bull airshow is on over the lake when you are there.
Krimml falls is well worth a visit.
Gross Glockner ok but can be busy.
Up the road towards Lofer are some lovely gorge walks (Klamms) and a cave, you can do them all on one ticket.
Hallstatt is about 1.5 hours away and beautiful.
There’s a great new restaurant in Leogang, Mama Thersl or something, right by the Asiztbahn lift (bike park).
For all mountain type riding, park at Schattberg Express gondola in Saalbach, get lift to top and do Hackelberg trail to Hinterglemm, then do Z-line there, then Blue Line, roll back to Saalbach and do Milka Line.
Leogang is great but more DH.
I’ll be there all Summer (15 mins up road in Maria Alm).