Don’t get too excited about the pencil museum - it’s just a couple of rooms plus shop and cafe but has a good quiz and drawing activities. Gets very busy when raining!
Boat trip plus picnic and walk eg boat from Keswick, get off Lodore Falls, walk as far round Derwentwater as you want, get back on boat at one of the stops on the west side. Or Aira Force, lunch at NT tea room, boat to Glenridding, walk back.
Lake District Wildlife Park much better than we expected - even my teenager enjoyed it.
Mirehouse in lovely setting with good grounds and great tea room, even if not interested in house itself.
Alpaca walking at Lingholm.
Definitely recommend Whinlatter.
Castlerigg stone circle worth stopping at for the setting - and potential for running off some energy and usually an ice cream van in lay-by as well!
Wray Castle is a non-stuffy NT place.
Lots of activities at Brockhole.
Just remember to take decent waterproofs and waterproof boots - we had a very wet week there in August with heavy rain every day. But Lake District still one of my favourite places!