How far can a five year old ride on a balancing bike?

Our family made the following cycling (not all) trip on Sunday. My couple and our five year old son. I am on a Tern Link C7. Wife on a Polygon Urbano 3.0. Son is on a loopfiets or balancing bike, or kid training bike.

I don't have a clear photo of the balancing bike now but it looks like this structurally, except without the painting in front, and the large wood plank for the cartoon head.

Update: just remember there is a photo of him riding on another trip:

Starting from Lorong 5 Toa Payoh, we rode to Lorong 8 for breakfast. Then we rode to Bishan MRT using the PCN and turn in from the path besides ITE. Thanks to Circle Line there is an entrance besides the bus interchange. I folded and pushed the two folding bikes using my DIY third wheel into the station and took train to Mountbatten station. Riding towards East coast along pavements (widening works is going on) is relative safe and easy.

First station is the Road Safety Park, which my son called it the fake roads. He like the place as he can ride by himself and role play. Next station Burger King to eat something. This is the first time he rode on the cycling track. Not too bad as it was around noon time though the whole day was cloudy. After filling our stomachs, we rode to the sand castle place besides the hawker centre. After some sand fun, we had some drinks and food at the hawker centre. Heading back, I planned to use the Siglap PCN to Kembangan MRT but mistaken the drain/canal as the one at Siglap PCN, and cross the ECP near car park E1. Luckily, it has a nice path leading all the way to Changi road. Thus, instead of Kembangan, we took train from Bedok MRT, change at Paya Lebar, alight at Bishan. Finally, although son was complaining very tired, we rode back home from Bishan MRT :)

Distance cycled ~15km. Zero incident.