Answer to Scenario 1: you can run a wire from a momentary switch to where the reset button would be. There is no real need to be concerned about wire distance. i ran a 16 foot 18guage wire from my trunk to my dash.
I actually did that weekend. i used to have to pull over on the highway and pull the fuse
Scenario 2 : i assume you will be running separate power supplies to each pc. IF that is that is the case, the DC-DC psu's have "ignition" connectors. they signal to psu to turn on wen it power has been applied. just like applying power to an amp
Thats how how i run mine, i have a switch wired up to the "ignition" line , i use it wen i am lending someone my car and i dont want time to use the pc. eg.valet
or in ur case for the kids.
last answer : i am not sure where the best place would be for a distro block.
historically, online prices have always been the best.
hope that clears up some smoke for ya..