We all LOVE salmon, so it's a bit hard to relate, but I'll try

.
First, the type of salmon. My favorite is sockeye because it has a strong flavor. Probably not the best for your dad. Look for Atlantic, Coho, or King.
Second, the cooking method. I prefer grilled or broiled, because, again, brings out the flavor. I would try poaching or a low/slow roast with a flavorful marinade. Some favorite marinades or toppings among salmon-non-lovers I've met or hosted are:
- Soy sauce and brown sugar
- Soy sauce, ginger and honey
- Whisk a couple tablespoons of mayonnaise together with lemon juice and some herbs (dill, pesto, or Italian blend are all good), press a thin layer on top of the salmon before roasting
Salmon chowder - make it like clam chowder, but with salmon instead of clams.
Salmon spread - make it like tuna salad, but with canned or 'cooked from fresh' salmon instead of canned tuna. Great as a sandwich, or a topping for crackers.