I have a black 2006 Macbook and I'm curious as to whether or not the charger for it will work with a Macbook Air. From what I've seen there don't seem to be huge differences between the chargers but I could be wrong.
As the Macbook came with a 60w charger and the Macbook Air only requires 45w, you'll be fine. If its a Magsafe 2 Macbook Air, you'll just need the Magsafe adapter
A higher wattage adapters will step down and charge other devices. Though I suspect that old Macbook is using the original Magsafe and not Magsafe 2. You will need an adapter for that.