Here is an educational kit designed to get your kids familiar with electronics. The littleBits STEAM Student Kit comes with hours of STEM material and 8 challenges to get students started. Users get to build self-driving vehicles, security devices, and other cool machines.
The kit comes with buzzer, fan, light sensor, button, power, servo, pulse, number, temperature sensor, inverter, and other bits. It also has servo mount, wheels, mechanical arms, and other accessories. Costs under $300 at this time.