There are great resources on the internet that can help you have a successful Family Home Evening.
I have found one in particular that has amazing resources for an emergency preparedness themed family home evening. There
are enough activities on the site, you could probably even hold 2 FHEs from the materials.
Go to lds.org for scriptures and conference talks on preparedness. Perhaps for a song, you can sing
Hymn # 303, Keep the Commandments. For a lesson that can teach everyone, you could use only what is in your food storage for
dinner and dessert that night. The activites on Fema's preparedness website for kids includes coloring pages, a scavenger
hunt, matching games, comics, crosswords, and more.