Kudos to you for getting the opportunity for a romantic getaway. Depending on what you're into, there are so many options. Here's a few ideas that I've done at different points in the relationship (depending on what I needed).
Eagle Ridge in Lake Geneva was AMAZING! it was relaxing, and romantic and quiet. We really got the chance to enjoy each other without any distractions.
Pheasant Run in St. Charles is great because there's always something to do. Spa, comedy club, bars, etc.
Otherwise you can turn any hotel room into something romantic. Set up your own romantic hideaway in any place you stay. Bring candles, music, arrange to have room service for dinner and breakfast if you choose. Make sure you have a hot tub in your room, wear the lingerie you never get to wear for fear your children will you see you in it and be scarred for life (okay, maybe that's just my own fear LOL).
Or even just relive one of your early dates. My husband and I used to do dinner and a movie every week when we first started dating. After having kids, we never did that! One day he just said, "Let's go on a date," and we went for dinner and a movie. When we came home, he had sprinkled Hershey Kisses from the door to our bedroom and had a sign on the door that said, "I kiss the ground you walk on." it was perfect. A simple night but very romantic.
good luck and let us know how it goes...maybe you'll inspire some of us!