I wouldn't bother disconnecting for anything. The roller coasters are all safe, and the people mover's magnetic devices are far too protected to damage your pump.
For rides like Kali or Splash Mountain, we also use a zippy bag in a spi belt. I would absolutely NOT put your pump in that middle compartment. I've had things get completely soaked in there.
Really, if you're using a spibelt and put it in a zippy bag, you're really keeping it away from any park water that you'll encounter.
You didn't mention water parks, but we tend to leave my son's pump in the locker, in something to keep it cool, and then periodically go back to the locker to bolus. But, he also doesn't develop ketones quickly, so we don't worry about it.
I do not believe that Medtronic gives a loaner pump anymore. They used to.