You're a parent. Worrying about your grown children and what kind of parents they are comes with the territory. But don't let your worries or desire to help get in the way of enjoying your family.
Have fun with your children in their role as parents. And have fun with your grandchildren. Share laughs with your child about the adventures and misadventures of being a parent. Be ready with funny stories from his or her own childhood. Think of enjoyable things to do together.
Be a real friend to your grandchildren. Get to know them as people. Take them to the park. Tell them stories. Laugh with them. They may turn to you later if they have a problem they are hesitant to discuss with their parents.
Make holidays fun, not stressful. Offer to host the family gathering if that works, but don't insist. Don't gripe if the other grandparents get the holiday visit. Figure out a time to celebrate with your children and grandchildren -- even if it's not the real holiday, or if you have to celebrate with different parts of the family at different times. Be a good sport. Remember what's important.