Vegies are great with kids as other posters have said. I am a serial plant murderer and have managed to grow these. We do it from seedlings. Have had lettuce, tomato, carrots, basil, sunflowers from seeds (kids loved these cause they were HUGE), strawberries and peas. We also plant lots of "potted colour" like pansies and petunias. Marigolds are good to plant around vegies as they deter bugs. Definately dig in poop! Makes a huge difference.
Good luck - my kids LOVE gardening and eating stuff they have grown.