Went with the kids whilst Interrailing, and we struggled to find enough to keep us occupied, in contrast to every other European capital I've been to.
It didn't help that it was bitterly cold, so there was no enthusiasm for the proposed trip to the Atomium. We went to the comic strip museum instead, which I enjoyed, but the DC were highly pissed off that it didn't have anything devoted to Tintin.
I recall food being difficult, too- we couldn't find anywhere cheap and good to eat- it was all quite formal, pricey sit down restaurants in the centre- so we subsisted on frites and chocolate, to the delight of the DC.