The are not minimum age exactly set for segway tours. But kids should be able to understand the rules and follow all the instructions of a trainer and a guide.
There is a minimum weight restriction for segway riders – 35 kg. Under this weight ride a segway safely is impossible due to technical reasons.
We use e-scooters and e-bike that are in bicycle transport category in Czech Republic.

To ride e-bike or electric scooter minimal age is 10 years, but in any case we will make a test-drive (free of charge) before you start.
The kid should be tall 150 cm or more to drive it.

Alternatively for kids we have mini e-bikes Xiaomi, so kids form 6 years can join segway / e-scooter tours on it.

Minimal age to drive a Trike is 18 years old, to go on the rear seat of a Trike the minimal age is 7 years old.
A idade máxima para ser condutor de um Trike é 69 anos, para ser passageiro é 75 anos.