although everyone is mentioning
Disneyland (california) I assume you actually mean you are going to WDW and on the
Disney cruise, what a lucky family!
there is a wonderful bunch of people if you go to the cruise board on this site that would love to help you surprise the family and can help you prepare for your trip.
As far as ordering things from Disney World, your best bet is to call their merchandise number (which I don't have handy at the moment) they will charge you the actual price (around $6 each) plus a shipping charge but no sales tax.
If you do have a
Disney store near you, it might be nice to wrap up some Disney Dollars that they could spend on the trip. They are charged dollar for dollar in $1, $5, and $10 increments.
Do they have any clue what a treat is coming their way?