No, it isn’t. But it’s fine, with caution. The two sections in particular which may cause issues with very young riders are shared with the red – the first bit out of the hub car park, called ‘The Snake’, which IMO is in really poor condition with some tight, potholed switchback berms, and the final little chute shortly afterwards down to the road across the reservoir.
The first you can avoid by heading back down the access road from the hub and turning right down the fire road to join up with the main route. The second can’t be avoided, but you might want to supervise closely at that point.
The rest is great fun for kids, including a couple of sections they’ve resurfaced relatively recently. The first of those (just past a long fire-road descent) is easy to carry speed into a steepish section with a drop off to the right, so the youngest again might need some speed control!
Avoid the reds there are some steeper rutted sections for tiny wheels, especially snake and swoopy
It’s easy to think the Snake is only part of the red, but it actually isn’t supposed to be!