Hello, Stacey!
February is a great time of year to visit Walt Disney World, as most days are far less crowded than during peak season and the weather is often far more temperate, too.
Because it's far less expensive to simply add another day onto your ticket than purchasing a single day pass, I suggest that you simply purchase your park passes with the total number of days you'd like to tour the parks (so add that extra day when you'll be staying at Disney's Port Orleans.) Then when you book your night at PO, add the Dining Plan onto your stay. Because you'll only be there the one night, I wouldn't bother to have the remaining day's worth of passes added to your Key to the World Cards, but you could if you wished to do so.
We usually purchase our park tickets right on
Walt Disney World's online ticket website. Enter the appropriate information for what you need, and you'll see how very reasonable it will be to simply add that extra day.
Have a wonderful trip! Be sure to send more questions as you think of them; we love to help!