Here's the application which will make this job easier for you.
Just need to create a group.
Add relevant members to the group.
Set up the task (type & time).
And VOILA! The app will ring the alarm at the specified time to all members at once.
Also, You are on your vacation, and don't want to get notified by reminders for the time being, simply deactivate yourself for now & others will know!
Log in with Google account
Refer Google Maps(Add task location)
Color coded events
Predefined set of task logos for visual appealing
Task completed, the task creator notified
Custom setting to manage the group
Custom view to schedule
All these at the tip of your finger!