For my parents 25th anniversary my husband and I went all out. At the time they had one child at home and lived in Central Washington.  We had them reserve a full weekend on their calendar and told them we wanted to come and spend the whole weekend with them and didn't want them to make ANY plans. Meanwhile we went to work arranging a great adventure weekend. 

They had a Fed Ex message delivered the Thursday before we were to arrive telling them that something came up and we were not going to be able to meet them after all, but they were to pack their bags ( we gave suggestions) and were to go to their friends place in the Seattle area. 

As prearranged they left their youngest with this family and the family gave my folks an envelope that gave them directions to a hotel. At the hotel a friend of ours met my folks with an envelope that had tickets, money and more directions for the next day. They rode the jet ferry to Vancouver Island in Canada. The directions they received took them to yet another hotel on the Island. 

Meanwhile; my husband and I had gone ahead and were running a step ahead planning their weekend and leaving notes.  The folks at the desk were happy to greet them with a note and prepaid suite. The folks at the restaurant were excited to help us out and explain that their dinner and the rose left at the table was all paid for. 

The driver of the horse drawn carriage had fun listening to my father in particular, who explained in detail all that had happened and that now he didn't know what more to expect because every time they went somewhere it was paid for and an envelope was waiting for them......