If they haven't been exposed directly to outside sun, then they will benefit from a gradual exposure to the sun. Just like people, plants can be sunburned. In plants, that can result in permanent disfigurement. In the case of cacti, they keep the same skin for years. Plants that grow new leaves all the time recover from the effects in time, but the scars left from too rapid an exposure to the sun can last the life of a cactus. They'll probably appreciate growing on the patio outside in time, just not all at once.
