Where can I buy second hand binoculars (for kids)?

Sometimes the ALDI and other supermarkets sell professional light weight great quality binoculars for around €10. You might be able to find some in the sales which start 1st July. There use to be a nature/ eco-friendly outdoor equipment shop on the top floor at City 2 near the very end of the Nieuwstraat in Brussels, so try there.

We bought binocs not too long ago in a camera shop in Leuven and were very surprised that they were much cheaper than we expected to have to pay.
Check out camera shops as a first step - I'm sure you will find something in the €20 to €25 range.

It depends what you want the kids to use them for. The requirements for bird watching, for example, are very different to those for general use, because one needs a wide field of vision, a good light intake and not too much magnification (8x or perhaps 10x is normal).

While good bird-watching binoculars are expensive, bird-watchers tend to look after them so second-hand ones are good value.

The small lightweight binoculars are almost useless for bird watching but are fine for general use.