I believe God can have a son. From my understanding, Jesus is a Creation of God. In the Bible Adam is called the son of God because he had no Father other than God. Jesus is called the last Adam, but instead of being formed from dust, he was formed within Mary directly by God himself, so he is the son of God- no earthly father, God alone is his Father.
I don't think this devalues him in any way. He is the perfect son of God, a perfect man made in God's image. God formed him and chose him to be our Savior. I believe that by believing(trusting) in Jesus, we in return have faith in God because for there to be a son there must be a Father and he proved to be the son by his works and resurrection. So we have faith in God by believing that Jesus was sent by Him if that makes sense.
I also believe that Jesus became a sacrifice for us and that through our faith in him, he will atone for our own sins. Through perfect obedience Jesus fulfilled his rolled and became our Savior. The Bible says that all things are of God and by Christ..this is kind of deep but to put it as simply as I can, all things are from God and reconciled by Christ.
Why? because it pleases the Father. It's hard to explain things clearly in a single comment but I hope I explained my point of view somewhat.