PART I, SUDBURY HALL: Actually, the 17th century Sudbury Hall and its (much later) enclosed Museum…read moreof Childhood are one item - but you can visit them separately, and pay separately. Of course, it makes much more "sightseeing sense", if such a thing exists, to combine the two - price-wise, it does too. You will still end up with a UKP 18.30 bill, which is quite hefty, and the reason I cannot award this attraction the full 5 stars.
Adults will find Sudbury Hall to be the far more significant one: A very fine stately mansion, owned and inhabited by the family who had it built in 1680-80 until the year 1969, when it was donated to the National Trust. Most of what's inside, in terms of furniture at least, actually comes from late 19th, early 20th century. But still splendid to look at. The main attraction is the astonishing 40 metres long Great Hall, which simply looks stunning and is filled with 2nd tier portraits of family members and (other) notables from the 17th to 19th century. The furniture you'll find in some rooms is a bit on the bland side, but there many interesting objects strewn around. There are very few art objects and paintings inside you'd recognize as outstanding; but then the Vernons didn't belong to the highest of nobility either. I've visited many mansions in England and Scotland over the past 10 years, and Sudbury Hall certainly sits on the lower middle end, three rungs below the most wonderful such place I ever visited, Castle Howard in Yorkshire. But maybe because it's not quite as refined as some others, it allows you an even more interesting glimpse into the everyday lives of the lower nobility.
The café is rather nice indeed, though usually as crowded and loud as the attached Museum of Childhood, as those will both be full of industrious little terrorists (i.e. children).
If you're in the Derby-Burton-Nottingham area and only have time to visit one country mansion, then I suggest you'll make that Kedleston Hall near Derby, which is far more imposing and luxurious. And easier to get to. Sudbury Hall offers a large car park that's a few minutes walk from the house. By bus, use the hourly 401 service between Tutbury and Uttoxeter.
PART II: THE MUSEUM OF CHILDHOOD: The Museum of Childhood is located on the grounds of Sudbury Hall (in the former stables of that mansion) - and if you're visiting the stately mansion, it certainly makes sense to include the museum in your tour. It covers two floors of various aspects of childhood (and the history thereof), but mostly focuses on toys of the past 200 years. And there are plenty! If you're at all interested in historic toys, you will find hundreds of those: Dolls, doll houses, board games ... anything, really. Some of them are so elaborate and precious you wouldn't let your own, or anyone's, kids play with them. It will probably cost you about an hour to sample the many exhibits, and while the place can feel a tad cramped (especially with that multitude of real-life little critters running about), it's a worthwhile addition to the main attraction, Sudbury Hall. Having said that, the price (even of the combined ticket) is a bit steep (hence, -1 star). I paid UKP 18.30 for an adult ticket to both places. You can unwind at a rather nice attached café, though when the place is busy, that one will be, too. Very helpful and friendly volunteers from National Trust running about. Unless you go there by car, take the hourly 401 bus from nearby Tutbury.