First, decide as a team what you want the goal of your FX to be - do you want to strengthen your current families, or do you want to reach out to new families? Also, perform a realistic assessment of the culture in your community. For example, is Wednesday night still known as a "church night" in your city? If so, maybe Wednesday night is good. If not, and if families have sports, lessons, and other programs going on Wednesday night, maybe you need to stick with a time on Sunday. For example, if high school football is huge in your community, it is not likely that families would forego the football game to come to your FX, so take Friday night off the table as an option. You might also pick a time when there is no other competing activity in your church (in other words, don't try to do FX during your adult Sunday school hour; it will be almost impossible to get parents to attend, much less
participate as actors, tech directors, etc.) If you have to move into what might be considered the lunch hour, bring in pizza or
sandwiches and allow families to enjoy a time of fellowship along with the program. Just try to start somewhere, even if it's once a quarter or a couple of times a year (around Christmas or Easter, for example).
In the first year: Use FX to launch the ministry season (it could take the place of an adult service or be held as a special event), then another at Christmas, and another at Easter.
In the second year, or if you have more resources: Hold your FX the first week of the month as a Family Night on Wednesday or a weekend evening.
As a final step: Hold a weekly FX at a regular time.