Expression "Full infinitive to"

Ok…Hi there!
When I say, “They don’t know how to dance”, I’m sure that the infinitive with how is ok. But I haven’t been able to come up with the usage for the inifnitve with who in a sentence.

I don’t know if this is o.k. “I haven’t decided who to invite to the party” Even so, is it common to use the full infinitive after the WH-question who? Because for me it’s much better to say, “I haven’t decided who I should invite to the party”

Thanks in advance…

Both are correct!
The difference is the added word “should”.

  • In “who to invite to the party”, there is some sense of obligation contained in the infinitive. This is the same sense as is conveyed by “should” in “who I should invite to the party”.

Infinitives with “to” may have different shades of meaning in them, depending on context.

  • I want to dance. (No extra shade of meaning.)
  • I don’t know what to do. (Equivalent of “…what I should do”: extra sense of obligation or “what it is best to do”. I think this applies to all indirect questions.)
  • Did you find any enemies to kill? (Equivalent of “…that could be killed”: extra sense of possibility, potentiality. The sense of the infinitive is also arguably passive here: the enemies are the ones that could be killed, not the ones that could kill. I think this shade of meaning comes to all infinitives that are attached as appositions to nouns or adjectives.)

hey Cerberus…thanks for such a smooth explanation!