First,

to DISboards!
What a wonderful adventure you are about to have!
You have already gotten some good suggestions and I am sure you will get more. I will second the comment of accepting that you will not be able to "do everything". Make a list of your "must do's" and then the list of "if we have time". DW and I have been to WDW many times and now are Disney snowbirds and there are still corners that we haven't explored.
Spend some time reading DISboards. Another favorite resource is the Unofficial Guide to WDW. The 2019 edition just came out. It is a big book and filled with plenty of great information all in one place.
You will visiting during Epcot's Food and Wine Festival which, if you are foodies, can be quite fun.
I second the "must see" Lion King show at AK. We think it is the best show at WDW.
Unless you are really into shopping I would skip Disney Springs for your first WDW visit. There is so much to see and do at the parks and there are plenty of shops in the parks.
One minor caution depending on what part of the country you are coming from. It will be hot and humid. If you are not used to tropical heat, plan for midday breaks. Or at least an extended lunch break in some A/C. Since you are staying on site consider taking advantage of the cooler morning Extra Magic Hour. You can get a lot done in that first hour and the following couple of hours before the crowds build late morning. Also be prepared for afternoon tropical showers. Have some ponchos ready.
One day if you think you need a break from the parks consider taking a tour of the monorail resorts, especially the Grand Floridian and the Polynesian. Easy to get from the MK.
Well, that's enough from me, I am sure others will have ideas...
Wishing you a

visit!