You can send notifications to everyone who is subscribed to your channel very easily.
To notify all members in your channel, click on the notify icon to the right of the channel name (only administrators can see this):
A lightbox will appear to enter a title and message:
Change the "subject line" and enter the information you would like to send to channel subscribers. Click send to send the message and then click "close":
All subscribers will receive an email from you with the subject line you select, the content in the message, and a link to the channel: