Check out this interactive planting calendar from Kids Gardening. You'll need to put in your last frost date (you can look yours up here), and it will tell you when to start seeds. Even if you buy starter plants, consider starting some things from seeds - it's a great chance for kids to be involved, and to see the whole growing process from seed to food!
Even before planting seeds, you can try making seed tape:
If you don't have a garden, you can still explore seeds! Start with a book - searching "seeds" on Growing Minds literature database gives a lot of ideas. Or explore seeds - sprouting them in a window, identifying what fruits and veggies have seeds inside, comparing seed sizes - so many opportunities!
Don't have any outdoor space? Try your hand at indoor gardening.
What are you looking forward to growing this year?