Tomatoes like chives and parsley and marigolds. Basil likes tomatoes. Spinach likes strawberries. Potatoes like beans. For many more companion planting ideas check here and here and here for teaching children
One little known fact is the finicky property of fennel. Fennel is beneficial to many insects and serves as a host plant for swallowtail butterflies. Finnochio Fennel is completely edible with delicious, healthy anise like flavor and is the smaller plant that develops a delicious bulb. Common fennel is grown as an herb. The only parts used on this plant are leaves and seeds.
However, the common fennel plant can also get 4-6 feet tall and spreads aggressively. Fennel is a real foe to tomatoes and potatoes. So keep your fennel in check or in a container. Be considerate of for your neighbors plantings.
And enjoy this herb's leaves and seeds and the caterpillars and butterflies as well!