Reservations prior to get to Japan

Hi,
We are arriving in Haneda Airport on May the 4th and have plans to take the Shinkansen Hikari Line from Tokyo to Kyoto on the 5th.
Can we make a reservation before activating our JRPasses?
The information says we need to do it 3 days before because of the holiday but we are not yet in Japan neither have activated our passes.
Can we do it online just with the the exchange order number? If so, how?

Thank your for your attention.