If it is just a simple, "one generator or the other, but not both" situation, then a slide or rocker in the breaker panel will work fine. Also, any manual transfer switch will work too. One generator would be hooked on the "grid" side and the other on the generator side.
What kind of inverter / battery charger does this feed?
As mary said, you'll only be switching the hot wires. All the neutrals and grounds are common and will stay hooked up.
The 120v generator will only power half the panel, and of course only send 120v out for charging.