Can’t help with ‘best’ perhaps. But for a 2wheel ‘Not park’ scooter, which does sparks (detachable):
http://www.amazon.co.uk/Razor-SK346-Spark-Kick-Scooter/dp/B002YT7YLS/ref=pd_sim_sg_5?ie=UTF8&refRID=0D5FVXYAABFSG0Y5BVHJ
Solid park scooters tend to be for slightly older kids/don’t adjust?
The ‘Micro’ two wheeler goes down well – as well, for more $$$. Each of these are strong and can 360 – but they do fold and are pretty twitchy straight after a 3wheel. The spark plate allens off -if it gets in the way of tricks. Although for a young 5 – making fire, might just be one of the best tricks anyway..
The generic park scooters go for 20 or so on Amazon if you search – all seem to be the same (more or less). The advantage is they are rated for 80kg+ though so you can do tricks as well 🙂 Even if jr struggles to reach the bars..