I need an answer from someone who is sure of the answer.
You ask the impossible. Nobody can be sure of the answer because the law is not clear. As far as I can tell the UI has no authority to dictate policies on weapons any more than any other entity. There are enhanced penalties for weapons offenses within a "gun free zone" but I'm not sure if the UI campus qualifies as one. This is not a ban for weapons outside a school or park, but instead it raises the punishment for any weapon violation. Personally I often drive through the UI campus with a firearm in my vehicle.
I am no lawyer so take what I say with that in mind. As far as I know there is no duty to inform in Iowa. If stopped then don't show your permit to carry along with your license like many others will advise you to do. If asked if there are weapons in the vehicle then shut up, the police do not have the authority to ask during a routine traffic stop and you still have the right to remain silent.
There is precedent that has made public roads and the right of way around them an exception to the "gun free zone" laws. A case I remember was an armed TV reporter that was arrested while standing in front of an elementary school on the sidewalk. He was not charged for violating the "gun free zone" law since he was in the right of way of a public road. It's court cases like this that has made the "gun free zone" law essentially meaningless. There is also a question on whether or not a university is considered a "school" under the law or is a separate kind of entity.
One other important point, it's not a "law" that says no guns on the UI campus. What they have is a "policy" of no guns on campus. It's going to be very difficult to make a weapons charge stick for someone that has a permit, not violating any other law or policy, while driving through campus. They might get you for trespassing at most.
I use "you" generally here. I know it's your friend but using the general "you" saves me typing.