I'm sorry, but how do you screw up a grilled cheese sandwich. I think they were the first thing that I was allowed to "cook" by myself, and I have yet to melt any spatulas in the process.
I let my kids make toasted cheese sandwiches in the toaster oven.
a) make toast.
b) put cheese on top of toast, and put back into the toaster oven.
c) when cheese starts to melt, take the toast out and stick the halves together.
It isn't rocket science, and the kids don't even need to ruin a spatula and a pan in the process.