I Want To Put A Family Reunion Together! How Do I Do It?

Hello,
Contact a small group of relatives, brothers, sisters, close cousins.  Use this group as your planning committee.  Make each member a committee chair person and delegate assignments.  Meet every other week and check on progress.
Reserve your reception hall or park at least 8 months ahead of time.  Get a broad base of entertainment.  Decide on the meals to serve and cost per plate.  Assign shirt colors to identify family members at a glance.  
Take travel into account.  Charge a minimal registration fee to offset the cost of the meeting hall, entertainment, music, meals.  
If folks are coming in from out of town, contact the local Chamber of Commerce and see about getting a discount from local hotels for ten or more rooms per night.  The more rooms you book, the better the discount.   
All registration fees should be in and relatives registered at least one month prior to the reunion.  This will give you time to finalize the details, sitting, meals, shirts etc.
Don't forget to plan on afternoon contests such as volleyball games, softball games, family history classes, show and tell about ancestors and such.  Keep 'em busy and make it fun.  They will want to know when the next one will be.
Good luck.  I hope it works out for you.