Depending on your budget, food tastes and how romantic of a restaurant you're looking for, I'd consider dinner at:
Graham Elliot
L2O
North Pond
Naha
Topolombampo
Bin 36

What month & day of the week will you be in the city?

On Wednesday and Saturday nights you can catch free fireworks off of Navy Pier (but visible from many locations downtown).

You still have at least a few more weeks for free concerts at Millennium Park.

A lot of the rooftop bars (which are often connected to hotels) offer a great view and nice way to unwind after dinner.