7 is great age in education. The whole world is interesting. Actually, the US ed. system in general does a pretty good job compared to international scores until about 8th grade. From then on, it is a struggle to make science relevant... which is why the speaker projects have been so successful. There has to be something in a physics course that makes a kid say to him/herself "this is cool, hmmm, this is what engineers do...hmmmm"
Volunteers can give kids insights into applications that they don't have the world experience to make for themselves.