We went last year and stayed in Windemere and loved it so much we are going for a long weekend this week! This time we will stay at the Inn on Ullswater to see a different part of the area.
When we stayed in Windemere, we did the boat cruise around the lake, got off at Ambleside and wandered around. We belong to the National Trust, and so we were able to visit Beatrix Potter's Hilltop Farm, and the Beatrix Potter Gallery in Hawkshead, where we saw a lot of her art displayed. It is gorgeous countryside, and thanks to the National Trust, it is not overly built up or commercialised.
This time, we plan to just hike, picnic and relax. We stayed at a B&B in Windemere, about 2 miles from the Lake, but there were lots of of B&Bs much closer and a nice little bus that ran right down to the pier on the lake.
I have no doubt you will enjoy visiting the Lake District!