Many thanks to @keanulatino for the heads to the site on twitter!
Stand Up to Cancer tweeted that Keanu Reeves will be appearing on the televised event on September 7, 2018. The event will air on CBS on at 8 pm ET/7 pm CT.
The Digital Live Show begins at 7 pm/4pm PT and will be streamed on twitter, FB and youtube. Note, I have no idea if Keanu will be present during this pre-show but it is possible there may be a glimpse of him on the red carpet.
The hour-long show will feature cancer survivors, influencers and celebrities, and offer viewers exclusive access to the SU2C red carpet and backstage areas in advance of the televised special.