Here's another Explora program that might be of interest, although it's not specifically geared toward homeschoolers. It's an afterschool program called Robo Task Force. Here's a description and a link. Sounds really cool.
"Robo Task Force is an after-school robotics club that offers transactive experiences for 3rd through 7th graders. Join other participants in exploring construction, materials development, electronics principles and robotic systems and design."