We don't have the ability to send a News Flash to just a group, at this time.
You could notify them about the survey, however, via the group control panel, under Manage Members. You'd use the "Notify Member(s)" option in the dropdown at the bottom of that page. They'd get notified via their chosen method for instant notifications: email, alert, or both.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .