i had the same problems with my old Socket Scanner (Barcode Scanner Bluetooth).
With the new Scanner they implemented a button to show / disable the iPad Keyboard.
There is no way to activate the IOS Keyboard in FMGo without this Hardware option on the Scanner himself.
Hope that FileMaker would bring us a solution...
The KSC300i scanners work the same way. A button on the scanner toggles the iPad keyboard's visibility.