As a member of the Sandwich Generation, you may be used to setting aside your own needs so you can deal with the challenges of children growing up and parents growing older. Taking care of grandchildren because your children can't, for whatever reasons, adds another layer to a sandwich that may already be difficult to digest.
Maintain a bond with your child's partner and extended family, even if, for the time being, you put these relationships on the back burner. By keeping the lines of communication open, your grandchildren will transition easier if they move from one home and family to the other. And a grandchild can't have too many loving arms.
There will be a huge void to fill and you may be confused about your role now. Don't be afraid to seek out a parenting coach or a family therapist. Although you likely were a natural when your kids were young, this is a unique situation. Learning skills and techniques from experts can make a big difference the second time around and talking with someone outside of the family about your worries and frustrations can be a lifesaver.
Do whatever is necessary to maintain familiarity and continuity in the lives of your grandchildren. By nurturing them and stabilizing their environment, they will begin to feel more secure. The structure in their lives and the support you give them will relieve their feelings of anxiety and stress. Children are resilient - as you model positive thinking and hope, they will thrive.