Say I have a search form and a booking form: is it good usability to automatically select all text in the input if the user taps them (to edit)?
In this case, you should meet your users expectations.
Text inputs are one of the most familiar UI elements, so doing anything out of the ordinary, will only increase cognitive load for the user - and frustrate them if the behavior is not what they intended.
Check what the native apps do on the tablet, and mimic that. (If you are using a standard control, this should happen automatically anyway).