Fuel used by either genny or tractor is fuel used. Use the tractor if you believe this is a rare occurance. No point in having a second genny even if you could find one during this outage. We have recharged with our truck with jumper cables even left the truck idling all night when boondocking in extreme cold. Didnt use any more fuel than a cheap genny would have.
Tractors do not have high output alternators, but your Deere should put out plenty for basic needs at a little above idle.
If you have a clampmeter to measure DC amperage, its easy to balance supply with load.
I would stay away from using an inverter unless you know the batteries are full, will have time to recharge.
