I have been to many seminars over the years (JJ Machado, Pedro Sauer, Dan Inosanto, Chai Sirisute, Guru Rick Faye, and others). Alot of the time the instructor will bring some of his higher ranking students and they will watch you roll and you can roll or spar with them as well, if they do come, then pick their minds as well as they more than likely have been with the head instructor for several years or more and will have alot to offer.
Usually around noon they will break for lunch which sometimes is catered or they have bag lunches for you which was included in the seminar cost, this is also a good time to meet the other participants and ask questions etc.
Just have an open mind and have fun, after all, that is what it is all about.