Tell us about yourself!
Drag, whether on the alternator or wind turbine will be minimal in both cases, just more on the turbine. You're already driving the alternator, so charging the batteries would be an inconsequential addition. When parked, the turbine would be the way to go. And you're not likely to overspeed it.
You'd have better efficiency charging the batteries off your vehicle's alternator. Drag will burn more fuel than the extra draw on your engine. Plus no rpm, charge controller or water concerns
One word - wheels. Two more - on everything.