When I was a girl, still living at home with my mom and dad, one of the treats we would make is homemade fudge sauce for over ice cream. I am pretty certain that the recipe came from the side of the Hershey's Cocoa Powder can. I am fairly certain that was a pretty simple recipe with sugar, water, cocoa powder, and vanilla. The trick to getting it right was cooking it for the just the right amount of time and boy, was it yummy!
Just the other day, I stumbled upon this recipe for fudge sauce. It is a bit different, but sounds good, too. It does seem to have quite a bit more sugar, so I am sure the younger kids will like it.
1/4 cup cocoa powder
2 T. butter
1/4 cup water
1 1/2 cups powder sugar
Cook until desired consistency.
The recipe did not elaborate on how to cook it. I suppose there would be no harm in just placing all of the ingredients into a small pot and cooking over medium to low heat. It probably should be stirred the whole time it cooks, perhaps with a whisk to keep the powdery ingredients from clumping. While you are stirring it would be easy to see when it thickens to the right consistency remembering that when the sauce is poured over ice cream it will cool and be even thicker.
If you try this let me know how it goes and if you liked it or not.