Grapes: full of children and grandchildren; Orange: good luck; Apple: safe and sound; Pomegranate: many children and many blessings; Jujube, peanut, longan and lotus seed: born early.
You can also put other things with good meanings, such as: sugar cane: meaning steady and rising; Pomelo: or honey pomelo, which means sweet and fruity; Banana: the meaning is like paint and glue, and life is sweet; Candy: sweet, sweet; Snacks: children will prefer them; Pistachio nuts, walnuts, almonds and other dried fruits: the collocation of daily fruit bowls.
As for which eight kinds to put, there is no clear regulation, as long as the meaning is good.