Reddit mentions: The best slot cars, race tracks & accessories

Just going to throw some ideas for products at you, please note I have no relationship whatsoever with them, I just googled for the kind of thing I think you're looking for.

Dirt cheap option: https://www.amazon.co.uk/Motor-Chassis-Encoder-wheels-Battery/dp/B00GLO5SMY

Slightly better option: https://www.dfrobot.com/product-367.html

Quite a nice option: https://www.dfrobot.com/product-426.html

Basically look for robotics platform/kits/chassis and not for RC cars for this kind of thing.

A few points, you probably want geared motors with encoders as the drive mechanism. Servos typically aren't continuous rotation. If you want the kind of wheel configuration of a road car along with encoders which are almost essential for autonomy I think you'll have to look at a custom build. Also if you're looking at self-driving then have a look at LIDAR scanners, not cheap but they'll allow you to do far more than an ultrasonic sensor.

https://www.amazon.com/gp/product/B07T8MBTMP/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1 I got these and they have been working good so far.

found it on amazon.... lucky!

Start with one of these for a chassis.

Add an arduino, some wires, some sensors. You're good to go.

Here is a link to the Hotshot Jr. It's just one of those slot cars however. OP used the shell for his creation. The other 2 shells are 3D printed.

http://www.tamiya.com/english/products/18624hotshot_jr/index.htm

You can find them on amazon.

https://www.amazon.com/Tamiya-18624-Mini-Hotshot-Chassis/dp/B0017TD8MA

That chassis is a LT832. Basically a Losi Micro-T clone.

Il y a même une version Mariokart ! Dispo sur Amazon JP.

I found this kit: http://www.amazon.com/gp/product/B00GLO5SMY?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s01

For $12 I couldn't say no. I got lots of stuff at radio shack's close out so I'm thinking of using a yun and motor shield to make a remote for it.

Depends on what type of extension you are using. I have seen a cord reel start smoking with only this thing attached to it because it wasn't unwrapped.

What's the goal of the workshop? To introduce programming? To introduce electronics? Does your target audience already have these basics down and you just want to cover some advanced control system topics?

(From experience these things tend to forget scope and leave attendees confused or bored. Or both.)

If budget isn't an issue and you don't want to focus on hardware buy some Pololu 3Pis: Arduino compatible they can work with C, C++, graphical programming and many languages.

Most of the time budget is an issue. If you're EE, take a look at the Harvard AERobot and build a few, they're pretty simple and cheap. (Or buy some: store link) They came from the Afron challenge:
http://robotics-africa.org/2014-design-challenge

No money and PCBs are too much work? Arduino + scrap electronics. CD drives, computer fans, etc. Or try this chassis, use a cheap motor driver design. I've done a similar workshop with cardboard robots, Arduino derivatives, motors pulled from scrap or surplus and simple IR reflectors bought in bulk (TCRT5000 are 10/$1 on ebay). Using a DC motor, a rubber band and food skewers in plastic straws you can make pulley systems that are cheaper than gearboxes. But these are neat. I didn't want programming to be a drag so we used Ardublock.

[Also: your Facebook group is closed, I couldn't see posts to make more accurate recommendations]