Your DS sounds like a really switched on child :-) the kind of child I'd always enjoy having in my kindergarten :-)
In Melbourne we have a place that recycles office and manufacturing off cuts and bits and pieces. Everything from electrical cable to timber and containers. It's called 'reverse art truck' and the other place is 'resource rescue'.
I wonder if there is something like that near you?? I think resource rescue delivers. Some tips also recycle bits and pieces and could be another option.
Giving him lots of bits and pieces would continue to challenge his creative inventive brain and is unstructured enough not to put him off. Frustration is a normal part of some children's learning.
There are some great factual books around that would also feed his enquiring mind but I can't thing of the name of them! If I do I'll come back and add the info.
REmida is Perth's version of this.