Pack some snacks and enjoy a relaxing family day out at Newlands Adventure Centre. There's loads of space for the kids to run around and get some fresh air.
You'll have no end of sightseeing choices when in Keswick. Newlands Adventure Centre is an ideal place to start here, but there are numerous other fine spots to experience. Derwentwater, Lodore Falls, and Buttermere Lake are not far from the outdoor recreational space and will fill in your day nicely.