You are going to be fine. You did a WONDERFUL THING HERE. JUST RELAX! Keep reading others' posts and threads. Many people have 2 or MORE! It is going to be a little harder at first. Wasn't it harder when you had your second child? I'm sure initially you will have more challenges, but it will pay off in the long run and they will become friends! (You may even be a little jealous of their relationship-LOL)
Have faith! Keep working!