controller for ping pong robot

Hi, i work in a school and run a table tennis club. i'd like to build a robot like the one in the link below but need to power five small motors. I can build the mechanical side but don't know how to get hold of or build a ac to dc controller able to vary the five motors speed independantly. Any help would be great as i've very limited electronics experience. Here's the link

https://www.youtube.com/watch?v=JkcnZ_2r5oI&feature=related