I did my very first trip to WDW in 2007. Solo - 10 days. Raised in Santa Barbara with 2 trips a year to
Disneyland until I was old enough to drive. Then 8 to 12 trips a year until I started working there at age 20. So I can claim to be a Disneyland veteran.
Clearly your time is limited because of the conference so most touring advice isn't applicable. You don't remember Carousel of Progress but it's a must see for DL folks. Same with Country Bears and the People Mover, so MK is a must even if it's half a day. You'll be fine missing most rides because the differences aren't that pronounced. 'though I always go on Little Mermaid because the line is SO much better than the one in DCA. If you can only get into one other park then it must be Epcot. Yes, Pandora is new and very nice but you could save that for a later trip.