Hi again Jeff,
I didn't read your post through thoroughly the first time, and noticed you ask about staying instead of driving home. One of the really cool things about seminars (for me), is the chance to meet and hang out with great folks, and thus expand my aikido horizons. I almost always stay with someone from the dojo that is hosting the seminar, because it is such a great way to get to know people (and of course, I reciprocate alot on that end too). Usually there is a party on Saturday night when theres a seminar, but you would be best advised to contact the host of the seminar to see if there are plans for any general party or not.
As to the comment about the Shihan always doing breakfalls; not so! There are so many techniques that don't require breakfalls, and the breadth of the knowledge of these teachers is so great, that you can go an entire seminar without breakfalls. Chiba Sensei rarely teaches classes involving breakfalls, whereas Kanai Sensei often has lots of highfalls, and Yamada Sensei seems to be in between. Don't be too nervous, it should be lots of fun.
Seminar is May 31-June 1.