I got some help planing our trip in this thread:
http://www.aikiweb.com/forums/showthread.php?t=7695
and in
this tread on Aikido journal forum
Corncerning Aikikai, we just went there for the morning class, and paid afterwards in the reception (I think it was 1500 yen for a class)
We really had a good time with Kato sensei (see the aikido journal tread)
Happy traveling
Michael