Well, I've never hosted, but I have lived with 3 different host families in my past study abroad experiences. Here are some things that made my stays pleasant:
1. honesty about whether the house was smoking or non smoking
2. when the families enquired about special diet or foods to avoid
3. being included in family activities, even mundane ones like grocery shopping
4. family took an interest in me, was patient in trying to make conversation in a foreign language, spent time together.

Another important thing is to establish expectations up front, like curfew, phone use, having visitors, laundry, etc, especially since your student will be so young.

It should be a fun and rewarding experience, hope you enjoy it!