you can buy gift baskets with romantic goodies & floral bouquets through disney floral at 407-827-3505 which can be delivered to your guest room.
you can also request a cake/dessert for special occasions at most wdw signature restaurants (i did this for my fiance's birthday at le cellier steakhouse in canada pavilion at epcot) by request in advance for a fee. his bday cake was like $16. mention when making your ps (priority seating) 407-wdw-dine. and at cinderella's royal table restaurant in mk, they do an anniversary table, all decorated & give you a set of champagne glasses for the occasion. (my parents did this years ago, not sure of current cost) and the character meals as well as disney dinner shows normally make a fuss over such occasions. chef mickeys does a special parade for bday/anniv guests my fiance did this on his bday it was so funny & was a great picture, the poly luau & hoopdedoo revue call anniv guests on stage for some extra attention.
another suggestion of mine maybe a night/day alone, they have in room babysitting, our family has used kids nite out & most deluxe resorts also have kids clubs with entertainment for a fee. have a couples spa treatment at the grand floridian 407-824-2332, the spa is a tradition of ours. do one of the wdw tours, we loved dolphins in depth at epcot where you interact with dolphins, in the water! backstage safari & years ago i went with my mom on backstage magic. i've heard the family magic tour at mk is quite popular with kids. 407-wdw-tour. or do a specialty cruise, we booked a romantic illuminations firework cruise on the breathless & ordered dessert & snacks through yacht club catering to have on board, it was fabulous! 407-wdw-play
happy anniversary! hope your family has a wonderful wdw trip no matter what you do for this special occasion!