Revised to straighten out pins that have PWM capability
EVERY new microcontroller project starts with a blinking LED. I have a 4 bit counter with 4 blinking LEDs connected to a CPLD sitting against my keyboard as I type. The universal "Hello World".
In the Arduino IDE, set up the board (with the board plugged in):
Tools->Board->Arduino/Genuine Uno While you are there, note the COM port
Now go to File -> Examples -> 01 Basic -> Blink. Compile and upload the file by pushing the round icon in the upper left corner with the Right Arrow (upload).
You should have a blinking LED. If this works, you have proven that a lot of things work. You have the right board, communications works, the board works, programs can be uploaded and, finally, the LED works. This LED will be a universal debugging tool!
At this point, you can try the Fade example for the LED, again in 01 Basic. You will need to hook up a resistor and LED as in the experiment linked below to pin 9
https://www.allaboutcircuits.com/projects/using-the-arduinos-analog-io/File -> Examples -> 03 Analog -> AnalogInOutSerial. This requires wiring up a potentiometer. Before you connect the center pin to the Arduino, connect the Vcc and Gnd pins and measure the voltage change relative to ground as the shaft is moved. It should move from +5 to 0V, etc. Use a digital voltmeter. If you don't have one, the Aneng AN8008 is a good entry point if you don't plan to use it on mains. It's perfect for kids. Anyway, connect the potentiometer, upload and watch the LED intensity change with the potentiometer rotation. The LED and resistor should be on pin 9 as given in the code.
Switch to the monitor Tools -> Serial Monitor. Make sure you have the proper COM port and baud rate (set baud rate at the bottom of the terminal window). You should get output data from the program.
The pins that will do AnalogWrite (fading) are: 3,5,6,9,10,11
https://www.arduino.cc/reference/en/language/functions/analog-io/analogwrite/At this point, you have a LOT of stuff working. Maybe it's time to follow along in the PDF file on the CD. The first experiment is a temperature/humidity sensor. Pretty simple! In fact, it's a lot like the AnalogInOutSerial example.
Here's the meter mentioned above:
https://www.amazon.com/s?k=an8008&ref=nb_sb_noss_1Instant delivery costs a little more...
I concede that the kit is a little advanced for an absolute beginner but the IDE has lots of Examples and there are projects all over the Internet. In fact, if you need help with any of the Examples, I wouldn't be surprised to find a YouTube video out there somewhere. The CD has complete instructions for installing the libraries and kit examples.
The Arduino is EXACTLY the right kit for beginners. They don't need a lot of electronics experience and most of the code is given. They WILL have to learn the C programming language when they branch out to their own projects; ''copy and paste' works well here! In a perfect world, they might have printed copies of the code they have already used in a binder. That way they can refer to it without jumping around in the IDE. The IDE does a lousy job of printing so copy and paste the code into a text editor and print from there.
Down the road, if the kids get interested in robotics, I highly recommend this robot:
https://www.adafruit.com/product/1639It is very FAST. Take a piece of white board about 3 feet square and use electrical tape to lay out a dog-bone shape in black. The robot will scream over the course!
https://www.homedepot.com/p/1-8-in-x-4-ft-x-8-ft-Eucalyptus-White-Hardboard-447562/204727075Most important: Have fun!
ETA: Don't be surprised if Sensors is less stimulating than something that moves. The DC motor, stepper motor and particularly the servo will probably be the most attractive experiments. Adding sensor (like object detection) to a robot will be a more interesting because it is an application, not a static demonstration.