My 17 m.o. son has just started having tantrums, which largely seem to take the form of throwing himself on the floor and banging his head. Usually he just does it once, realizes it hurts and then cries more while I comfort him. Unless I think he is going to seriously hurt himself (for example, the floor is concrete), I don't initially try to stop him, as I want him to feel free to get out the frustration that he's feeling. My DH, on the other hand, thinks we should always intervene and stop him from hitting his head (maybe by saying something like "I know you're frustrated, but maybe you can try stomping your feet instead" -- which is what I typically say to him once he's calmed down). I'm worried that intervening right at the beginning of the tantrum is just going to communicate to him that it's not okay to let out his anger, frustration, etc.
Is there a good way to intervene to make sure a toddler is not going to hurt himself but still allow him to get out his frustrations? Can anyone reassure me that he is not going to knock himself out?