A go-to simple recipe that I use all the time with my 17 and 12 year old boys is Buttery Cooked Carrots that I lifted off of AllRecipes.com some years ago. This is as simple as it gets and it has butter and sugar, two food groups that kids love.
Here's the ingredients with the carrots in a steamer already going (I was running late this week). The recipe calls for boiling, but I thing they get a little too water logged that way. I retain about 1/2 cup of the carrot juice water for use with the recipe.