My grandkids and parents visited Warwick Castle last week and weren't that impressed and felt it was very expensive for what it offered. They described it as a 'tourist experience' owned by the Merlin Entertainments Group who also own Madame Tussauds.
Near by is Kenilworth Castle which is a ruin but has links with Robert Dudley Earl of Leicester and Elizabeth I. He spent a fortune restoring the Norman castle to make it suitable for her short visit.
https://www.english-heritage.org.uk/visit/places/kenilworth-castle/
There is also Baddesley Clinton which is a wonderful moated manor house just north of Warwick..
https://www.nationaltrust.org.uk/baddesley-clinton
Have you thought about Blenheim Palace? Winston Churchill was born here. This is one of the great treasure houses of England and the inside is sumptuous. The grounds are equally as good with the water gardens and secret garden. There is a miniature train to the Pleasure Gardens with adventure playground, maze and butterfly house. The grandkids loved this and preferred it to Warwick.
https://www.blenheimpalace.com/
Chepstow castle has already been mentioned and I love this. Castell Coch is a bit further to drive but is everyone's dream of a fairy tale castle with its turrets.
https://cadw.gov.wales/visit/places-to-visit/castell-coch
The inside is a C19th extravaganza designed for the Marquess of Bute and is fantastic - imagine the Arabian Nights... Have a look at the pictures here.
https://www.pooky.com/inspiration/we-love-interiors/amazing-interiors-castell-coch
Cardiff Castle is similar and also belonged to the Marquess of Bute. Both of these knock spots off Warwick Castle!
https://www.cardiffcastle.com/