There's one in every group - even if it is only a group of two- the Eye Closer. And if someone isn't blinking, they are looking off to the left. Or right. Anytime you're trying to get a group pic you can count on one person having their eyes closed. So here's a tip I'm passing along for you, and this is not my tip, it comes out of a Scott Kelby book I have, but I have tested it and it works. Here goes:
Have everyone close their eyes and tell them not to open them until the count of three. When you say three you hit the shutter, maybe even a micro-nano second before. Not only does everyone have their eyes open and looking at you, they also usually have pleasantly-surprised wide open eyes which makes for a nice pic.
Try this and let me know how it works.
What eye-opening tips do you have?