The amount of misinformation about guineas on the Internet is astronomical. I, too, have read that guineas have to start eating within 6 hours of hatch. Nonsense! And I just had a guinea hatch two days ago - on day 20. The other 27 eggs are just sitting there, waiting for a more reasonable hatch day. Meanwhile, the lone little keet has the brooder all to himself, and seems to be doing just fine. Guineas write their own rules.
And for the record, you can find an amazing amount of misinformation about chickens on the Internet, too.