For a vacation for 2, I would recommend tennesee. The mountains there are amazing, plus, there a large assortment of shows to see.
Also, Chicago is nice, but Its not exactly a place you'd want to stay at for more than a week.
Correct me if I'm wrong, but there's caves close by in Tennessee/Kentucky as well? And one of the largest aquariums, Ripley's Aquarium - it looks amazing, and is definitely on my list.
http://www.ripleysaquariumofthesmokies.com/
If you go in the fall, I think the colors are quite amazing. You could get some camping and fishing done too - I'm hoping to go myself this year.
Or you can stop by and see us, on the gulf coast nearby Florida, but with it's own "flavor."

I can hook you up with some rates if you call Caribe the Resort.
I think the best trip I've ever taken in the USA was inside my state of MI, to the Silver Lake sand dunes. We camped for 4 days, but had some friends who had a Jeep and went dune buggying. I've been on the tallest/fastest rollercoasters, etc., and that was STILL the most fun I've ever had. It even rained the whole time, but the sights were gorgeous, and recklessly bolting over a hill of sand at 60 mph, without being on a track or anything, it was totally awesome.
Bet there's cool things to see in New York too though.
If you've never been to Cedar Point in Ohio, and you like rides... everyone should go at least once in their life.
