You will love Yamada sensei. I wouldnt worry about being called up for ukemi. Usually one of his "guys" will be there or a dan ranked uke will be chosen. But he does stop class alot to give out pointers, so you may get lucky and get the honor of taking some brief ukemi for him if he stops at your practice.
For seminars, make sure you bring more than one Gi. There is nothing worse that coming back from a lunch break to a wet Gi. Also bring some extra underware. Sweaty underwear is no fun for the drive home. Bring a towel and soap if there are showers. Bring a towel anyway to wipe sweat off with.
If you are injured, make sure to tape your injury and point out the injury to your partners. No point in paying for a seminar, then get hurt and have to watch from the sidelines.
Grab as many Dan ranked students as you can to practice with. Yamda sensei changes partners after every technique. So its a good opportunity to work with the Dans.
For my own practice, I would to try to train at the front of the dojo/seminar, so Yamada sensei would see me. If he comes over to correct you, thats a good thing. You getting your moneys worth and a small private lesson from a one of a kind Sensei.