On stored water, which is the cheap answer and the one I would sort out this month regardless of what you decide about a generator.
Separate drinking from flushing. They have completely different requirements and storing everything to drinking standard is why people give up on this.
- Drinking and cooking: food grade containers, kept somewhere cool and dark. A few days worth per person is a reasonable target and it fits in a cupboard.
- Washing and flushing: anything clean that holds water. Drums in the garage, a covered butt, containers under a bench. Quality barely matters and this is the bulk of what you actually use.
Rotate it. Label with the date, use and refill every six months. Water does not spoil in a sealed clean container, but containers and lids do, and the rotation is what keeps you honest about whether the arrangement still exists.
One thing specific to wells worth knowing: when the power comes back, run the taps for a bit before drinking. Pressure changes and a pump restarting can stir up sediment. And if there has been flooding as well as an outage, that is the situation where testing before drinking is genuinely warranted rather than cautious.
Also worth doing now while it is calm: write the sequence down and put it in the kitchen. In the dark on a Thursday evening nobody remembers that filling the bath is the first move.