Ideas please - 80th birthday night away

[GRCP]

Parents are both turning 80 this summer. We are taking them for a night away, need it to be in a location which is within a 2ish hour drive of SE London.
Somewhere enjoyable for 80yos, 40yos and kids age 8 and 10. Mum HATES the sea. We all enjoy history, they love plants/gardening. Some nice shops etc would be good, nowhere too busy (not central London).
Any ideas?

Stratford upon Avon?

Stamford- you can walk round Burleigh House, lovely grounds and playground for the children, can also visit Belton house and Grimsthorpe castle as all nearby

Both great ideas, thank you - will take a look

Salisbury (& Stonehenge)?
Winchester (& Marwell Zoo)?
Stratford upon Avon (& Warwick Castle)
They were the places we went with grandparents for 70th or 75th bdays
Cotswold Water Park might be an option if you want to rent somewhere. Lots of places within a few minutes drive as well as a swimming pool, tennis court & things on site.

How about a river cruise and meal up the Thames, some of the vessels are now equipped with an 'open to the early hours' nightclub

Edit: please ignore, just read your post again