K.L.
Why would you want to give him lactose free milk if he is not lactose intolerant? It is not only more expensive, but lactose free milk goes through quite a bit more mechanical and chemical processing to remove the lactose from it.
If he is only going to be drinking lactose free dairy products, when given full lactose dairy in other situations, he may develop a sensitivity: not an allergy mind you, but the body becomes "used" to what you give it, and regular dairy might start to give him gas, constipation or diarreaha. There are also many health benefits to full lactose milk, so why ruin a good thing?