The City of Davenport was absolutely correct in doing so. From the Iowa state constitution:
"Religion. SEC. 3. The general assembly shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; nor shall any person be compelled to attend any place of worship, pay tithes, taxes, or other rates for building or repairing places of worship, or the maintenance of any minister, or ministry."
In other words.. ALL Taxpayers (and city employees) must be represented… under the State Constitution. Davenport simply was following state law. It should be renamed. If you as an individual wish to refer to it as "Good Friday" because it agrees with your faith.. then no one is stopping you. But the City of Davenport represents a wide variety of people besides those in organized religion.