I only have one grandchild and it would be a miracle if I ever had a second - but I think it's similar to the "reaction" of having your second child.

As far as the adults go, Chatty has a terrific idea. Do something that will help them out NOW - and don't worry about "comparing" what you did last time. As far as the child goes - if you did something special - a special momento or legacy for the first grandbaby - then do something similar for the second. That way there will never be that - "grandma loved me best" - conflict between the two siblings