I highly recommend having a back-up generator from the start to save your RE battery from being deeply discharged. Its my understanding that if you are now connected to the grid, you can use that to top off your RE battery pack when there is no wind/sun.

If you have no grid, a back-up generator is a vital piece of equipment (IMHO).

That being said...first I would get a large chest style freezer (opens like a laptop computer), and attach additional insulation. Put a couple of jugs of water in there, and during an outage the block ice will extend its usefuleness.

Bar-be-que some freezer meat the first day of an outage to make room in the freezer for some of the more sensitive or expensive items from the fridge that are slowly warming. You can even go "old-school" and put one of your ice blocks on the top shelf of the fridge to help it last longer.

Concerning the lawn mowing tractor; lawn mowers are thrown away on a regular basis. They typically have a clogged air filter which leads to a rich carbon-fouled plug. This results in hard starting and difficult pushing from the dull blade thats never been sharpened. After 3 years or so, no one pays $50 to have someone fix it when they can get a new one for $150, so, fixable mules can be found in the trash for free.

There's a dozen examples on the web where someone has taken a free lawnmower, fixed it them selves, and attached a pulley set that spins an alternator to provide 12 volts.

Your riding mower has a bigger engine than most push mowers. It would not be difficult to temporarily remove the blade and attach a pulley set (in an emergency) to run a fairly large generator head.

The famous Amatek (and other Permanent-Magnet-Motors / PMM's) are fun wind projects, but are not huge power producers. Perhaps a similar PMM/3-phase servo motor would be very useful for this purpose.

If you think this would work for your situation, of course you would need to fabricate mounting brackets with a control panel and then test the output, so the set-up would be standing by when such an emergency hits.