Not sure if you can rent annual spots for an RV around the Coralville Resevoir, but there is plenty of water and a lot of areas where you can find good water. I'm from NE Iowa but live the Twin Cities. Still make it down for IA football in the fall and boat with friends out of North Liberty on occasion. I do know that you can put an RV on Lake Delhi for the season. (or at least you used to be able to) Maybe check into that one too.
Good luck and let me know how it turns out. BTW- Hawkeye football in the Big Ten almost worth the move in and of itself. IMO.