bring a guitar (as long as you aren't worried about getting it damaged) as that'll make it a lot more interesting... small amp wouldn't hurt either (if you have one- one of those wee microamp type things).
don't get too in-depth, i mean plenty of guitarists don't know the difference in tone between alder and mahogany etc., so i doubt a non-playing audience is going to care either. difference between fender and gibson sounds would be a good idea, though, show how it's brighter with a fender, and darker and more distorted with a gibson- the rg1570 should let you do that (assuming you have an amp with you). pretty much what 38th and twin said, in other words, but probably don't go too deep into the construction and specs.
up to you, of course, at the end of the day you know what your lecturers are looking for and we don't... :)