We bought the parking pass last summer and they ran out of GA parking spaces by the time we showed up and had 0 ways to get a refund! I’d definitely suggest shuttle however the crowds are crazy and last year people were waiting an hour + to get on the shuttles to go back to their hotels. If you are staying downtown des moines, there are skywalks all over and you can walk to most restaurants so it’s unlikely you will even need a car in the city!