Bee asked
The question is, how many unvaccinated kids are there, and how many does it take before they are seriously at risk of having their own little epidemic?

The answers depend on the particular disease as population desities, inubation times and transmissability (infectiosness) all vary. For most of the diseases above I believe the threshold of "vaccinated" is ~85% for prevention of transmission through a population. If fewer than 85% are effectively immune then most of the diseases above will remain endemic in the population.

The debate about "individuals' rights/responsibilities" vs "communal rights/responsibilities" occurs in many guises and contexts and will probably continue for as long as there are more than two people left on the planet.

Cheers, Rowan