I don't think mini-kegs are actually a very good packaging solution, for commercial beer.
Unless you invest in a proper mini-keg tap, with co2 bulb (if you're not a home-brewer kegging your own, that's just not going to happen), you have to use the basic plastic tap that comes with it. Then you end up with 5 litres of beer, in a keg but it looses carbonation as the volume remaining inside drops and you have to drink it all in one night or it will go off.
Another problem is that the mini-keg is designed to dispense with the keg upright, so you have the choice of chilling it in the fridge and then removing it for serving, or removing shelves from your fridge, so you can stand it upright and dispense beer while keeping the beer cold.
They are fun for a party, but I don't think you will ever sell the volume of beer you would shift if it were in bottles or cans.