For one thing, you should expect about six phone calls from them (three on Friday, two on Saturday, but only one on Sunday)! Also, you should expect to be rather tired by Sunday night. And, if you're like me, expect that in the future you'll want them to go away frequently so you can have your granddaughter for a whole weekend.
Seriously, make sure that they leave you some written information about her daily routine, what she likes and doesn't like to eat, when she goes to bed and takes naps, how she is bathed, her doctor's telephone number, and so on. Chances are you already know much of this, but a few written instructions are helpful. Check the answer given on this web site to a mother by Dr. Karen Sokal-Gutierrez who wanted to know what information should be provided a babysitter. Even though you, as a grandmother, are much more than a babysitter, you will still need the same kind of information every dependable sitter should have.
As for what to expect from the child herself, a great deal will depend on the kind of personality she has already developed and on her relationship with you. If she is a secure and happy baby, knows and accepts you, you can expect her to show little emotional reaction to their departure. If she is fussy and irritable, never comfortable except when her mother is close by, she may cry and resist comforting for a long time after they leave. This reaction is less likely than the first, however. It should be a great experience for all of you—your granddaughter, your daughter and her husband, and you.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.