My 9 year old son wants to bui

My 9 year old son wants to build a robot that would capture rain through the top of his head, have it travel to the cavity of the robot chest where the rain water would then be filtered and then travel out of one or both arms, could be hot and cold, but only room temperature water is need for his project. The arms then could dispense the water into a drinking cup. He would like to build his robot and would like it to have some type of track wheels in order to move out into the rain, collect the water, then filter for consumption. To me it sounds fairly simple but robots are new to me as well. If you can help we would be very thankful.

Steven