The Galveston port is not quite as busy as Miami. There are only a few ships in port at a time. Carnival has the first pier & Royal Car. has the second one. You will have a great time.
This link is very interesting & it has a port camera for Galveston. In the view, you will first see the restaraunt then beyond that is Carnivals terminal & a little further down is Royals. Depending when you view, you can actually see the ships in port.