iCloud account(s)

Here's the situation:

1x iMac (shared)
1x iPad (shared)
2x iPhones (His and Hers)

I want to share contacts, calendars, and bookmarks. I don't want to share iMessages.

What's the best way of achieving this? One iCloud account? Two? Three (his, hers, and shared)?

Answering my own question then, I think I need to use one iCloud account and specify the 'Receive at' addresses on each device correctly and I should be fine...

Yep you can add as many iCloud accounts as you like then choose which services to enable for each account. iMessage and FaceTime can be set independently.