My DS didn't have cereal as a first food but from about 7 months he had baby/toddler muesli mixed with a small amount of milk and mixed thick, rolled into balls and eaten as finger food (BLW here too).
It's not a must but I don't think you have to totally cut it out either, if he eats a better lunch with a smaller breakfast maybe just reduce the amount? I know I wouldn't want mine to fill up on cereal and not get whatever I was offering for lunch if I was balancing food groups and variety across the day/week.