Peggy, I have two words for you - I'm jealous!! Did you say you would be on a cruise? Ahhh...wind blowing through your hair, tropical drink in hand and pure bliss! Oh, I'm sorry, let's get back to your question!
Yes, someone could definitely make your Advanced Dining Reservations for you! They can be made online or by calling 407-WDW-DINE. Just make sure the designated person has your name, phone number, restaurant choices and dates/times, the number in your party, any celebrations (anniversaries, birthdays) and your resort reservation confirmation number - if staying at a Disney resort.
I would suggest doing an Excel Spreadsheet with all of your first, second and third choices and times - just to make it easier on the designated person. If you are doing any dining experiences that require pre-payment, don't forget to leave your credit card information!
Have a magical day and let the memories begin!!
Ca'Sandra