How do you Set up apple ID / iCloud for family?

I have an Apple ID along with an iCloud account. My wife also has her own ID and iCloud account. We have two young kids that are starting to enjoy games, movies, music, etc... Currently we have 3 iPhones, iPad, an iMac , and Apple TV.

Both my wife and I have been purchasing apps separately but would like to share the apps with all of the devices. (We are both currently using the same music and photo libraries). Even with a family account it is important that my wife and I maintain our own contacts and mail and iMessages.

I like the idea of setting up a new Apple ID but get a little confused when it comes to iCloud.

Should I create a new Apple ID for the family and use one of the current iCloud accounts for the family purchases? (or get a third iCloud account?)

If we go with this new shared account idea, is it possible to still load some of the apps that we have already purchased, or do we have to start fresh and re-buy the apps that we like under the new account?

Seeing the majority of apps have been purchased under my Apple ID, it may make sense to use my iCloud for all of the purchases but don't want to share mail etc with my wife or kids?!? I'm confused.

Thanks in advance for you help...

TY