Hi Bob,
Just to clarify - are you saying that if we arrive on the afternoon of March 23 and get our JR pass, it will be difficult if not impossible to make reservations upon our arrival for four nobinobi zaseki seats together on the Sunrise Seto the next evening (March 24)?
Yes, the changes are against you. As there's only one train per day, seats are very limited and often sell out way in advance. You can always try but expect a "No seat availability" reply.
Are you also saying that if we have friends in Japan (we do) who can make a reservation for us, that those reservations can be made locally and then picked up when we get to Japan, and they will be covered by the JR pass?
Yes, this would be possible. Basically, he/she would need to call the JR Reservation line. Then get seat reservation tickets for the Sunrise Express but explain to them that the other parts of the fare are already paid (covered by the JR Pass) and then pay the reservation fee by phone (that would only be a couple dollars per seat), then collect the tickets in Japan and give them to you before boarding. As you can see, it is quite complicated and it has been a while since I heard somebody pulling this off.
Kind regards,
Daniel