It's a horrific attack with awful innocent deaths at the same time that any conventional attack that achieved the same impact on Hezbollah would have been even worse for those around them.

That there was collateral damage is unfortunate, but Israel was definitely not indiscriminately targeting civilians, which is what would make it terrorism.

This was a surgical strike that happened to have some unfortunate collateral damage. Well within the accepted rules of war.

   Rule 12. Indiscriminate attacks are those:
   (a) which are not directed at a specific military objective;
   (b) which employ a method or means of combat which cannot be directed at a specific military objective; or
   (c) which employ a method or means of combat the effects of which cannot be limited as required by international humanitarian law; and consequently, in each such case, are of a nature to strike military objectives and civilians or civilian objects without distinction.