We visited Chatsworth on route from Scotland to Cornwall. We stayed in Sheffield which is about 30 minutes drive.
There were 4 people myself and my wife my father in law who is 90 and a friend who is 82. We enquired before we visited to see if we could use one of their a mobility scooters for father in law to help him see the house and gardens. Unfortunately they didn't have a scooter available (they only have 3) but were happy to provide a wheelchair. This came with the added advantage of my wife's admission ticket being waived as a carer.
We spent the whole day at Chatsworth and had a marvellous time. The interior of the house is magnificent with treasured art works at every turn. The staff are all very helpful and happy to answer any questions about the Devonshire's extensive collection. We took nearly 3 hours to wander slowly around the house. The gardens were interesting and we could have spent a lot longer getting lost but it was a lovely sunny day and we preferred to sit and enjoy the views.
They run tours of the garden by golf buggy at additional cost.
There are various catering options which are reasonably priced. A food stall next to the main house and the Stables complex with buffet style and waiter service restaurant.
Everything considered we had a great day and would thoroughly recommend a visit to Chatsworth.