I have had several apple cash transactions that I didn't authorize happen. how do I set it so I have to double click on my ipad to authorize transactions. need to know how to stop apple cash from using face ID on ipad.

Do you have Accessibility or AssistiveTouch features enabled? The default is to double click and confirm with Face ID or Touch ID.

<<Confirm the payment

• • iPhone or iPad with Face ID: Double-click the side button, then use Face ID or your passcode.
  • iPhone or iPad without Face ID: Use Touch ID or your passcode. 
  • Apple Watch: Double-click the side button.
  • Mac with Touch ID: Follow the prompts on the Touch Bar and place your finger on Touch ID. If Touch ID is off, tap the Apple Pay icon on the Touch Bar and follow the prompts on the screen.
  • Mac without Touch ID: Confirm the payment on your Bluetooth-connected iPhone or Apple Watch. Make sure that you're signed in with the same Apple ID on all devices.
  • Apple Vision Pro: Double-click the top button, then use Optic ID or your passcode. 

When your payment is successful, you'll see Done and a checkmark on the screen.>>

Make purchases using Apple Pay - Apple Support

Face ID is a lot more secure than a double-click, not sure your issue is due to Face ID. Wondering if the cash spend identifies the specific purchases?