It reads:

Unconscious characters cannot quest, attack, defend, collect resources, trigger abilities ...

The silvan mechanic returns "an ally you control" with events.

The same with dwarfs. (like when you control 5 or more dwarfs.)

Will this work with unconscious characters?

Yes, in both cases. You still control characters that are unconscious even though they can't do the various listed things. So unconscious Dwarves still count towards you controlling 5, and unconscious Silvans can be returned to your hand.