Can i give my 3 wk old formula mixed with cereal?

our new born seems to just get hungry all the time. we started from the start with 3oz. a few days later 4oz then 5 then 6 now its about 6 oz every 2-3 hours. some other parents have mentioned to start adding some form of cereal with her feedings at night so that she may sleep all night, what do you think?