From the Disney Parks Blog page: #AwakenSummer at Walt Disney World Resort
Also beginning Memorial Day Weekend, guests will be able to enjoy many of the park's existing attractions in the evening hours for the very first time. Kilimanjaro Safaris will be open for guests to get a glimpse of the savanna's animal occupants as the sun goes down, and of course guests can rediscover favorites like Expedition Everest and Primeval Whirl in the dark.
The park hours have already been extended, which means FastPass+ plans can be made now in the MyDisneyExperience App.
Two new F&B locations, Tiffins restaurant and Nomad Lounge, will also open their doors on Memorial Day Weekend. (Reservations and dining packages haven't been released yet, but as soon as they are we'll post an update).