Coming in from the east you should be fine. The Channelside area where the port is isn't really effected by Gasparilla as far as closures or detours. The road closures and detours start more just outside the port area to the west near downtown and South Tampa / Bayshore area.
With that being said be prepared for the crowds and traffic it brings....
Gasparilla Tampa is one of the largest pirate parades in the United States. And, it's more than just a parade. It's now a festival with several events leading up to the Parade of Pirates' main event. An average of 300,000 people attend this event every year, and many people attend it every year.