The app will run on ALL iPad models currently available.
WiFi-only iPad models (ones without cellular network capability) do NOT have a built-in GPS. Your only option if you have a wi-fi only iPad is to use an external Bluetooth GPS receiver.
Note also, that WiFi-only iPads do NOT have a compass sensor built into them.
There are a number of external Bluetooth GPS devices available. Obviously, you need to evaluate these devices yourself to ensure that they meet your requirements. Hema make NO recommendations regarding any external products suitability for your intended purpose.
Here is a couple of suggested devices which you may find useful:
The Bad Elf range are stocked in Australia by the online retailer The Flight Store at the Gold Coast Airport.
There are also some units made by Garmin, which have been used with success by customers, such as the Garmin GLO: https://www.ja-gps.com.au/Garmin/glo-bluetooth-gps/
Try a Google Search for GPS devices to use with your Wi-Fi only iPad, as the product range is changing all the time.
Even though the cellular model iPads are the only ones which have built-in GPS circuitry, you do NOT need to have a mobile data plan and / or SIM installed in the iPad to use the iPad app. When you install the app, the maps are installed along with it, so there is no need to "stream" the maps off the internet while the app is in use.
The app does NOT require an active internet connection while in use.
It is wise to be sure that the iPad you are considering purchasing suits your needs. If in doubt about particular model specifications, check on the Apple website or search Google for more information.