Mindstorms or compatible programmable Lego

Ebay.

Does he have any already?

The other issue is that they live in Australia so ideally something available there rather than shipping from the UK.

He doesn't have any programmable/coding type stuff but my engineer brother is trying to steer him that way now.

Arduino?

I think Arduino/Pi etc are too advanced for him at moment. He's at the tail end of Lego, - im thinking something in-between.

I've found some Lego clone Boston Dynamic style motorised dog kits.....just not in Australia😖

My eldest has Lego boost which uses a form of scratch for programming but is a step simpler than mindstorms. The programming also works with the newer Lego motor systems (I can't remember whether it is power functions or power something else) so that you can for example program a Lego train to take a colour and distance sensor on board to work as signals (at least that's what my train addicted child did). Basically any of the newer app compatible power / motor systems from technic to trains can be programmed using scratch and an iPad or phone. I don't pretend to know all the details or how to do it was worked out. We got a book and the Internet showed the rest.
Hope that helps or at least opens up things to look for.
Edit: powered up is the stuff to look for now power functions (sorry). I think all the app controlled Lego uses elements of it.

we use lego mindstorms ev3 , they also have lego spike kits but not as advanced. There is also fischer technic https://www.fischertechnikwebshop.com/

Looks like Lego boost is no longer available as well😖

Lego powered up stuff is great. Nice app with an intuitive interface that you can either use with prebuilt systems (eg the big Liebherr excavator, we mainly use it for trains though), or to create your own using the exactly-like-scratch interface. Works best on an iPad or tablet, but can be used on a phone.  I don't think there is a fire kids version. Good online community of resources as well - both for programming and for suggestions to automate powerless systems. We powered the Hogwarts Express & have plans to work on my PistenBully.

We really like it. There was a bit of backlash from the previous power system users as the two are not compatible. At all.

The flippable tank thingy looks lush.

I think Arduino/Pi etc are too advanced for him at moment.

If you buy a full kit, the code is supplied.

The actual build is pretty straight forward, he might need some help with some of it.

The Arduino stuff is simpler than the Pi stuff.

Freenove do some decent kits. Ship Worldwide as well. https://www.freenove.com/

Re. Mindstorms, I bought myself the kit years ago as I like both Lego & robots 😀 I was pretty disappointed tbh. They've made the programming side very easy but have done nothing to address the fact that designing & building a complex machine out of Lego Technic is [I]incredibly difficult[/I]. So once you've gone through the example builds you kind of run out of good stuff to do, other than motorising existing Lego kits I guess. At least I did. Possibly if you're an engineering genius you'll take to designing your own bots etc better! Technic Lego is also really expensive (especially their motors/sensors etc) if you want a decently wide range of parts.

That itch is scratched for me now a million times better with a 3d printer and basic electronics stuff (which is also a million times cheaper than the equivalent official Lego part!) such as Arduino (though I much prefer ESP32 now or even Pi Pico).

I’ve found some Lego clone Boston Dynamic style motorised dog kits

Where abouts in Aus are they? If Melbourne then they could have a chat with metro hobbies, they have quite a lot of Lego stuff