You do not have to pay a cellular charge with a WiFi equipped iPad, although some retailers will activate it when you purchase. All you need to do is go online & suspend the service. I purchased mine from Apple, and used it for 8 months before I activated the Verizon service. The GPS works fine without cell service, while using a non GPS equipped version for navigation will give you a fairly accurate location as long as you have an local WiFi signal, it won't be usable outside of a WiFi connection where the GPS versions will work anywhere as long as you choose a navigation program that doesn't require a cell connection (such as CoPilot).
One note - if you plan to use the cell connection in the future, be sure to choose a carrier that covers the area you plan to travel in. The Verizon & AT&T iPads are not interchangeable - they have different radios in them...
