I want to recommend Kentwell Hall in Suffolk for a day trip, or even as part of a weekend away!
I'm a bit biased as I'm one of the volunteers who works there but I'm also a nanny so I have a bit more of a critical eye on it children wise!
It's a manor house which at certain times of year is brought to life how it was in the 1500's. it's currently filled full of Tudors (300 ish of us) and will be open to the public over the next 3 weekends. (School parties on the week days with a home school day on Wednesday 3rd July contact kentwell for more details)
Tudors will be going about their everyday life upon the manor- whether that's as a blacksmith, baker, spoon maker, builder, archer or even as a wealthy family member in the house itself. You are encouraged to discuss all elements of their lives with the Tudors, either to do with the work that they do or where they live, and also to have a go at many different parts of Tudor life! It's a very immersive experience and is packed full of education about the Tudor times, as well as family entertainment!
The main event (on at the moment) is the largest event that Kentwell does, but we also have Tudors there at Easter, May Day, August and September, Victorians there in August and December and very scary Scaresville in October (NOT child friendly)!
There are many local b&b s which are brilliant and reasonably priced if you wanted to make a weekend of it. I can recommend The Cock Inn in Glemsford which I have stayed at twice.
Hiya, reading your post made me feel all nostalgic! My family are from long melford, i lived there when until i was 2 and then mum wanted to come back up north. Dad was born and bread there. Lovely to read it is still an impressive place to visit.