Here's another youth option for kids. It's basically a strider bike (low, with no pedals) that has an electric motor too. It's not cheap ($600-$700), but it looks like a great way to get your 3-8 year old on a motorized ride!https://stacycstabilitycycle.com/
'Your child can learn to push, balance, and coast in the Non-powered mode. Graduate them to the powered mode (the holy grail of fun) as they show proficient use and understanding of the brake and the ability to coast and brake while standing. Start them with a speed similar to what they can push the non-powered version at, and they learn the use of the twist throttle, and a long coast turn into a constant use of throttle and giggles."