Advice please for travel in obon

Advice wanted please. A family group (9 adults, 4 children) needs to travel from Tokyo to Tomamu (near Sapporo) for a wedding on the 8th August which is the start of obon week. We will arrive in Tokyo around the 4th. We have used JR rail passes previously but timing may be tight for bookings this time. Internal air travel using an Air Pass is a problem because of the blackouts associated with obon etc. Any suggestions would be most welcome.

I have no complete understanding of the dynamics of Obon traffic yet, but I believe that this year (2009), the weekend of August 8/9 will be most busy for "outbound" traffic (leaving Tokyo), but that the traffic situation before August 8 should not be extreme. I don't think that you should have problems making seat reservations for some trains, arriving August 4.

However, the train journey from Tokyo to Hokkaido is very time consuming. For convenience, I recommend to fly. It might be possible to get a relatively cheap flight from Tokyo to Sapporo in combination with your international air ticket.