Consider addition of a small plot devoted to native and polynesian introduced plants. Recommendations:
Native - Mamaki primary food of the Kamehameha butterfly
Palapalai fern used for decoration for hula
Polynesian introduced - Dry land Taro
Ipu gourds used for dance
Teaches history, environmental concern, conservation

Green beans are easy and grow fast enough to keep the kids interested. Squash and pumpkins are good ones because it really gives the little ones a sense of pride to grow something that may weigh more than they do.