What is an easy way to reduce a boronic acid to borane?
LAH will attack the boron-oxygen bonds without going after the boron-carbon bond, see here (Eq. Z, p. 142).

But it also deprotonates the hydroxyl groups as a strong base like a Grignard reagent. You need to prevent that.  Convert your acid to an ester (OH -> OR), remove the water and then apply the LAH.