Hi
We have a mud kitchen (Here we call them 'Bush Kitchens'
)
We have the kitchen situated near our bush tucker garden so the children can freely use the plants.
We recycled a microwave, hob, tyres, planks and heaps of pots and pans etc
Changing children isnt really an issue (our children are 4/5) and we encourage them to hose themselves off before comming into the bathroom to change clothes.
Not sure what particular rules you feel the need to introduce in a mud kitchen? Surely the expectations of children in this environment would be the same as in any of the other areas within your setting?