You do have lots of choices. The easiest and cheapest is to pop your hood, attach the charger to the truck battery and charge. Yeah, I would start the truck after a couple of charges to make sure the battery is ok. The generator is a viable alternative. I don't think charging 3600 mAh batteries is going to strain the truck battery, but better safe than sorry. Sending DC to an inverter to convert to AC that powers a DC power supply for your charger seems a little complicated. I usually try to take the simple route but you need to do what you feel comfortable with.

Depending upon how often you want to fly you probably need two or three sets of batteries. That way, one set is always charging and you can fly often. An alternative is to get LiPo's which will charge more quickly (45 min - 1 hr), or A123 which charge very quickly (15 min), but you purchase convenience and speed with $$$. Maybe that's best left for later when you get more deeply into the hobby.