Honister slate quarries are well worth a visit, really spectacular. There's also a via ferrata if the weather is clement.
Boat trips on Windermere or Ullswater, either hire a skiff or go on a cruise round Belle Island.
Kankku in Windermere, hire an ex-MOD Land Rover 90 with satnav and do a green lane safari round the south Lakes.
DO NOT be tempted to do Beatrix Potter, it's garbage.
Shiela's Cottage in The Slack, Ambleside, for good scran.
The Glassworks in Ambleside (near the car park) for glass blowing and lovely gifts.
Skiing on High Raise if there's snow.
Windermere Steamboat Museum was good but currently closed.
Booths cafe at Windermere station and Lakeland just behind, good cafe also, shop is full of solutions looking for a problem.
And of course.... mountain walking!
Old Dungeon Ghyll and New DG for some mountain inn ambience.