Mini Bike Upgrade

Hello OldMiniBikes'ers

I received a mini bike about 10 years ago, (I thought it was a Bonanza, now leaning towards a Trail Horse) it had a B&S 3hp with 6" wheels on it and worked fine for my son, but not for me and it's been sitting for the last 5 years.

So now it is time to upgrade it so we can both ride it.

It now has a new HF Predator 212 (still needs mods to work).

But I have questions about the wheels/tires before we go any further.

I bought 2 - 13 in. Pneumatic Tires with White Hubs.

Can I add hydraulic disc breaks to both wheels easily?
Axels are 1 1/2" and to short to use as is.
Rear wheel will need a sprocket, 2 piece is what I was thinking. Again, how to add this ?

Parts are what I'm looking for mainly, and some pointers would hurt.

Thank you all
Hi. I'm not a vintage guy,but you should post pics here so people can see what is ....use the 4th icon on top of post that looks like a stretched canvas and choose upload from computer tab and choose pic and click upload ...