Whipsnade Zoo is also 20 minutes.
Bletchley Park, Home of the code breakers, is 25 minutes. We really recommend doing the afternoon tea (you will need to book) the ambience, period music, furniture, crockery and even the waitresses are all in period costume. You will probably need 2 days and your pass is valid for an entire year
Leighton Buzzard Narrow Gauge Railway. is a ten minute drive.
Quainton historic steam Railway Centre and Quainton windmill.
The Roald Dahl Museum. A very interactive experience. Free entry.
Tring Natural History Museum. 10 minutes away. This museum of stuffed animals was a gift from Lord Rothschild to his wife. Free entry.
Aylesbury Theatre is just 10 minutes drive
Odeon Cinema and Ten pin bowling are 10 minutes drive away in Aylesbury
An indoor Go karting track. 10 minutes in Aylesbury
Milton Keynes is a 20 minute drive and has a whole array of attractions, Locked in Escape room, indoor ski slope, indoor skydiving, cinemas, theatre, restaurant and of course it's famous shopping centres.