My almost two year old has been "helping" in the kitchen since she was just over a year old. She is very task oriented and helps clean up, sweep the floor, wash dishes and load the dishwasher.
I use the normal precautions...keep her away from the stove and isolate all dangerous utensils (can opener, knives, melon baller--it has a deceptively sharp edge) isolated in one drawer so they don't get mixed in with regular spoons and spatulas.
From the start, certain cabinets have been off limits and since she has her space, I rarely even have a problem with her getting into what she shouldn't.
A four year old should already have a good grasp of "hot" "cold" and "no". Save for an accident, it is perfectly safe for your son to participate in meal participation and clean-up...you'll be happy later if you start building helping habits now.
You need a good, sturdy non-slip stepstool or two and a little patience and creativity. Let him stand at the sink and "wash" dishes. Give him some kid-size pots and pans (IKEA has great kids kitchen accessories) and some of the food you are chopping to mix and cook on his own.
It is not paranoia to want to keep your kids safe, but we can wrap them in bubble wrap either. Teaching safety now will keep them safe later.