In the first few days I'd make this menu for the five meals - as my five tips:
For breakfast, a cereal with raisins in (and if your child has a sweet tooth then add honey).
For lunch, a peanut butter and jelly sandwich with great peanut butter and fresh brown bread.
For afternoon snack an apple in slices, and some banana too.
For dinner, baked beans on toast with a nice sausage or a poached egg on the side.
It's still short of greens, but there is protein, carbo's, fruits, grains (pulces).
It's a beginning.
You just never buy pre-packaged foods again!
If you make soups, you can make them together...they taste great and are easy to make.
Try one new green vegetable a day.
All the best.