Your broken iPad TouchID button will require repair. It is a common misconception that an iPad (or iPhone) can remain fully functional with damaged or defective physical buttons. The Top button of your iPad fulfils multiple functions, including the biometric TouchID sensor.
Whilst Accessibility features (such as assistive touch) can be used to augment the User Interface, these features cannot be used as a substitute for physical button sequences that must be used to trigger system recovery actions. Sooner or later, you may encounter a situation from which you cannot recover.
Until repaired, you may not be able to resolve a locked-out (disabled) iPad - or reset a forgotten device passcode.
iPad Repair & Service - Apple Support
Before committing to the cost of repair, which without benefit of an AppleCare+ plan will be substantial, you might be best advised to have your iPad assessed at the Genius Bar of your local Apple Store or Apple Authorised Service Provider (AASP) - where you can explore your available options. You may decide that replacement of your iPad may be more cost effective:
Genius Bar Reservation and Apple Support Options - Apple