Keep calendars and alerts separate 2 users

I have a Macbook Pro Hubbie has an iPad & iPod. I would like to keep his calendar items and alerts on his devices and my events and alerts on the Mac while also syncing iTunes between all devices & syncing his calendar and events between the iPad & iPod. No matter what I've tried I can't keep them separate. He's on the iPad before I'm on the Mac so I don't get the alerts, and he wants the iPad & iPod calendars/alerts synced. Any help would be appreciated