Congratulations! As the father of two boys, I can say its awesome. The best part about it, and its esp sweet if you have boys imo, is that you get to re-live your entire childhood but remember it and make it better... ie you wanted a huge train layout when you were a kid, have at it.
i started my oldest on model trains (w extreme supervision) at age 4. good times...
relax, and enjoy the ride. oh yeah, get your sleep now!!!