I didn’t see any references to the Dolphin or Swan resorts on Disney’s website’s brochure for the dining plan. Can you not use the plan there?
You won’t see it on Disney’s site because the Swan and Dolphin are not Disney hotels.
In fact, Swolphin’s restaurants do not participate in the Disney dining plan, nor can Swolphin guests buy the official Disney vacation packages.
Swolphin guests can not charge parks, shops, or restaurants back to their rooms, other than those shops and restaurants located in Swan or Dolphin and Disney guests can not charge anything at Swan or Dolphin back to their Disney hotels.
Swan and Dolphin have their own dining plan, but it is very limited menu wise.