Cereals are very light are best for dinners. This is because when one is going to bed it is expected that one stay clear from heavy food because it tends to dulls and weaken the body the following day. Medically, eating of heavy food is not recommendable because the food may not easily digest before one goes to bed. With this said eating of light food like cereals is not bad
My child used to eat cereals for dinner (not because we are in short for money, but if that is what child wants to eat, why not? its not an every day dinner meal in the end) but it does not end good, because in few hours child is hungry again, but because it is considered as dinner, my child prefer to take snacks and sweets before night sleep, instead of eating proper food.
Cereals are light, but are digested fast, and cereals are totally not enough to wait 10-12 hours before breakfast. For me cereals are more like snacks than a proper dinner, lunch or breakfast. It is only something that you might take if you are really hungry and cant wait for a proper meal.
Dont forget that not everyone eats plain cereals, like default Kellogs Corn flakes. People prefer to eat cereals with cinnamon, sugar, chocolate flavors and additions, etc. Its a lot of sugar. So its a portion of sugar after which you will still be hungry shortly for dinner. Think about it.