In the scenario of 4 people driving EV's and charging them (I took 4 from "...a surburban family with mom, pop & children all driving EVs". Well, it's possible to charge them all at once at least with the power service I have, but I wouldn't recommend it. Especially not all of them using 240V chargers. I guess the 120V chargers would be enough to get Johnny and Jane to school and back, given that my 120V charger gives 6 miles for every hour charged, but charging at that slow a rate results in a horrible conversion loss going from AC to DC. So using 120V chargers too often adds to your power bill way more than what you get out of that power. That means you're left using 240V for almost all charging. And even that is also better when you set your EV to charge as fast as possible (mine about 9.5kW) instead of the lowers (about 5.2kW), again because the faster charge rate = higher efficiency in conversion from AC to DC, which means charge them at 9.5kW whenever possible.
If all 4 were to charge at 9.5kW at the same time, we're talking a total of 38kW just for charging. Can your panel handle it? Probably yes (100A service X 480V on 2 legs = 48kW). But that leaves only 10kW left for the rest of the house, which ain't much (my clothes dryer draws 6kW when running on high, and my old A/C unit would draw 4kW, then there's the oven, stove, and whatever else the family of 4 has turned on, and the incidentals we forget about like all the electric clocks and the internet equipment, etc. So no to charging all 4 EV's at once unless you drop the charge level lower and make it less efficient. Perhaps the best way is to charge them only 1 or 2 at a time. And you can do that unless all 4 family members each came home with a completely drained EV late at night and needed a full charge by 7 AM in the morning. EV's have scheduled charging to allow you to use off-peak hour rates. Each EV owners could schedule his EV to charge at times different from the others. To replenish the charge from a day of 30 miles of driving, my EV would take a hair over an hour to charge at the highest speed from my home charger.
As far as "...the insurance companies will note these systems and surely raise their rates accordingly." Not in my case. When my wife and I sold her old used car and decided to replace it with a new EV, her insurance went up only because we changed the coverage from liability only to full coverage, and because the replacement cost is higher (the EV cost more than a comparable ICE car). That's it. There's no EV surcharge added to either our car insurance or our homeowners insurance. (I did raise my home owners coverage to higher amount to account for replacement cost increasing both from property values going up anyway, and from the solar and EV equipment added to the house. That raised my premiums, but again, not solar rider or EV charger rider added.)
About Scenario 2: Yep. My kids are grown and moved out, before EV's became a thing. But given how often my kids offered everything in the pantry and the fridge to their friends I have no doubt they would have done the same for free EV charging. LOL You can pay a little extra for chargers that require passcodes (think apartment chargers). But I don't know much about them.
About upgrading the electrical capacity to a neighborhood if a lot of EV's are charged there: yup! That is definitely an issue.
Does any house have 480v service?