Sounds great to me. Here's a thought for you to consider. Have the students design and create what this crowd would call a "franken bike". You or they can pick a frame and clean it up. Then select parts that will work on that frame and work together to make a bike with a certain goal in mind. Like a commuter or a cruiser or racer or whatever, I think it's good to have a goal. If you have the space, draw out the frame on a table and layout the parts in their specific locations as they are collected. It seems to me there would be so many different problems that would need to be solved that it would be challenging and with a goal in mind a real good project. To me it sounds like a lot of useful fun.