Not related to a Dingo, the kart has no step down near the seat and it does not gently incline towards the front. Its a newer styled Manco one seater, it was before they switched to Subaru Robins engines so that places it in the 90's. Good find.
Carb troubles, its a smaller choke styled carb, if you've cleaned it once and can get it to run that means it has some debris left in the carb from the old age and time it had set up, lucky for you gasoline itself is a solvent, the more you run the kart the better it will get, if you want you can put a cap full of carb/injector cleaner into a full take and run it with that, I've found that sometimes cleans things out. While we can clean the jets and the carb as a whole, there are check balls in these carburetors that are impossible to get to and just need to be ran to clean them out. Do not add much of the cleaner mind you, just a small amount, I use a cap full and thats it.
As far as live axle goes, if you ride it on concrete you want to stay with one wheel drive, your turning radius will be severely hurt once you switch. If you ride off road often, it may be something you want to look into, but keep in mind, if you have 2 children this is just one kart, do you really want to drop over 200 dollars switching axle, tires, wheels, brakes, sprocket, etc for one kart? On that note its a short kart, that also may mean you dont want to spend more on it, this is a great kart for the age group they are in but might want bigger in the long run.
This is your owners manual -
http://www.tricountysupply.com/pdfs/IPLs-103-103_9290R3.pdf
Its an entry level kart, does your happen to be equipped with the gear reduction unit?