How wonderful!
I agree with Sally. Also, I think it's nice for exchange students to be introduced to their host families' regular everyday lives. If I recall, you're quite new to gardening yourself. (?) What else do you usually do that you could introduce them to?
Do you live near a big city? They'd probably love to see that to compare to home, but especially any natural wonders in your state. Being from a small island, the wide-open spaces of the west might be especially awe-inspiring.
If this is an ongoing, organized exchange program, you should receive a lot of guidance ahead of time. Have fun!
