Is it possible to configure things such that iPad gives me an option to open the Camera app to scan a QR code to connect to a Wi-Fi access point? Do note that the iPad will be enrolled into DEP and this is required during the initial setup.
It is not possible to access the built-in Camera app before the initial setup is complete.
As the iPads in question will be configured via DEP, the appropriate approach would be to provision for your device to join the desired Wi-Fi access point(s) automatically via your MDM solution. When done, the iPad will automatically connect to the said Wi-Fi network if it is available, even during the initial setup.