Anniversary Dinner in Mississauga??, Quiet, two people, romantic, great food and atmosphere??
It will be on a Saturday night.
Head down to Port Credit; lots of options there. Colossus would be great, it’s Greek food. They have excellent Greek wine as well. Get the saganaki! Flaming goat chz, yum! There is also Italian, Aielli Ristorante, and Hooks Grill for seafood. I would definitely make a reservation with any of these places.
I haven't been in a few years but you might want to check into Barbizon restaurant at Hurontario & Eglinton. http://www.dine.to/barbizon I was not a fan of Lago when I had dinner there, but have enjoyed Aielli Ristorante on Lakeshore. If you end up at Aielli, order the chef's 3 appetizer plate. Last time one of my apps was bison.
Verdi on Derry Rd would be a perfect spot. Very good Italian, nice room, great service, quiet, romantic. But, it's north-east of the airport which is far from the residential areas of Mississauga, which are more south-west of the airport.
I've only been there for lunch, if you are interested you might want to make sure that they are open for dinner. http://www.verdi.ca/Ristorante.html
Piatto on Dundas just east of Mississauga Rd(Erindale Park area) isn't bad--usually quieter than the PC joints on a Sat. nite, too.