Yeah, Sentinel killed Ironhide like that because Ironhide was the strongest one of the autobots there.
If a 'hero' goes down like that and you feel attached the movie did its job. I think it was a good move in the movie to kill Ironhide. A pity was that no one said something about it, even a brief mention. Especially from Optimus when he returns.
Another pity was that Dino, Sideswipe, Ratchett & Bumblebee did nothing after Sentinel drove into the building getting his things back. Proper autobots would try to stall him untill Optimus would arrive (where was he anyway?).
Back to 'feeling the death' : I had a difficult moment when Soundwave was ready to blow Bumblebee into oblivion. It went like "No no no" in my head. heh. Even though I knew Bumblebee couldn't be killed.
Kids at TF movies:
In the Netherlands the movies have a 12+ rating.