Yes, it sounds like this is a reasonable setup, and should work work pretty much as you describe it, all without any programming.
You do not necessarily have to use 12 V DC pumps, but I would recommend it. 12 V DC water pumps are plentiful, quiet, and inexpensive– many are used for applications like desktop PC CPU coolers.
Also, I wonder if there might be good alternatives to requiring a button press to reset the demo. For example, you could have a small hole in the pipe that drains out the water over the course of a minute or so, even if they don’t press the button to reset the exhibit. The kids would still see the water standing there, unless they were quite patient to wait for it to drain all the way. With programming, you could also change the “reset pump” controller to be triggered by the two main buttons, but not to run the pump until after a delay of (say) 30 seconds.
