I may be misremembering and anything can change, but I believe the Expo is open until 8:00pm on Thursday.
I don't remember what time it closes on Friday, but possibly 8:00pm as well.
The day you really need to be concerned about is Saturday because the Expo typically closes early, maybe around 4:00.
I'm attempting to figure out how to balance the Halloween stuff I'd like to try and the 70th anniversary stuff I'd like to try. Maybe the 70th stuff waits until the
Disneyland Half next year.