If you decide on taking a cab from the airport then you should notice a sign inside of the cab that states the fixed price from IAH to downtown. Usually a small savings off the meter but it seems the taxi drivers never seem to remember the fixed rate if you don't remind them. For things to do you might check the website for Discovery Green as there is often evening entertainment in the park. The park itself is literally across the street from your hotel. You can take the metrorail to the museum district for easy access to the museums near the train stop but it is too far to walk from the train stop to the Menil museum.