Wheel magnet sensor counter for measuring how much you bicycle

Hello everyone
In a school project we have to make solutions (to even small problems). Our subject is: To get children to exercise more. We thought about connecting an Arduino to a bicycle and have that bicycle have a magnet mounted on the wheel. That way the Arduino could count rotations, then that number of rotations would be stored on a USB drive. So that we could connect that USB to a computer, where there is an application that would give a respons to the distance traveled with the bicycle, that would motivate the child to exercise more.
But unfortunately my group and I are quite new to the Arduino and thought that some of you might be able to help us out.

Is there a way to design a Arduino system in Live Wire? If yes how?
What type of Arduino is recommended for the mentioned purpose?`
Maybe we should take into account the radius of the bicycle's wheel, so that the distance could be calculated with the simple formula: 2piradius*rotations. We think that the radius should be able to be entered somehow. Is it best to leave that to the computer application?

Thanks in advance :smiley: