Not to dampen your plans, but I don't find La Tavernetta to be the least bit romantic. It's loud and hurried, and the food swims in too much red sauce which will stain that new dress she's sure to wear for the occasion. Erwin's nice, but if you drink at all there's little chance you'll get out for less than 35 dollars per person, even with the coupon. Forget Bistro Campagne - it's definitely beyond your price point.
My suggestion would be Katerina's, which serves very fine, reasonably-priced Greek food in a sophisticated setting, accompanied by what is usually excellent, dinner-conversation-friendly live music.
A publication I'm embarrassed to admit I read once wrote something like "Katerina's is the kind of place you wish existed. Thankfully, it does." I agree wholeheartedly.
Katerina's
1920 W Irving Park Road,
773 348-7592