I would suggest you purchase LEGO Mindstorms EV3 for your kids. It naturally leads into TETRIX and FTC competitions. Get the educational version from www.legoeducation.us
It is available for pre-order as it has not yet been released. It will be awesome. Many different models will be coming out with apps and it is open source with a LINUX system. Check it out on the website.
coach FTC #5887