How do I stop other linked devices joining the same network when I use keychain?

I have a Macbook pro, iphone and iPad all linked with iCloud and I use keychain for credit card purchases.

However I believe Keychain also shares wifi log in passwords with other devices - so my portable mobile internet device and my iPad and iPhone automatically join that wifi network but I only want the Macbook pro to join that one.

How do I stop the iPhone and iPad from not joining that particular wifi network?