Your 7+ year old is now beginning to have a variety of favorite tastes and unfortunately for parents, the snack or meal liked once will not be liked the next day. But as a parent you need not worry; instead of looking at one meal which they did not have, look at the overall food intake of a day and a week to check on the nutrition they get into their system.
What you need to know
The most common topic among parents of 7-8 year olds would be regarding food - what their kids eat – or rather do not eat. Many children are fussy eaters. Although earlier they would be willing to eat what their parents fed them, by 7-8 they will have their own taste and likings.
Balance consumption of fruits, vegetables, whole grains, meats, low fat, calcium-rich foods over a week instead of concentrating all of it in one day. Let them pick out the fruits and vegetables they like from the market/vendors and engage them in the preparation to some extent so that they will know what they are going to eat. It surely helps. Also note that peer pressure often makes them have preferences for certain foods.