There are always seats reserved for persons with disabilities in every class of service. The SK DK agent simply managed to get UA to assign these.
Strange that SK doesn't interline with DL for ETKT or paper TKT. PTA with DL should be possible against a fee too.... these are all basic TA training stuff.
Hope all goes well. Don't worry about the seating issue. I'm sure the GAs will make sure everything is fine.