The redirection protects both you and your creatures from the source. If the source would deal more than X damage to multiple objects, you decide which damage is redirected until X is used up. For example, your opponent casts a spell that deals 1 damage to you and 1 damage to two of your creatures. If you cast Shining Shoal with X = 2, you can have damage to you and one creature redirected to the target, or you could have damage to both creatures redirected.