Choose a time of year/ month where the weather is relatively cooperative.
Find out if people want to come with or without ktheir kids, school schedules.
I live in a vacation spot. Find a spot where there is a variety of lodging or someone with a HUGE lawn, and good septic

where everyone can pitch a tent.
Then see who's interested.
Look for things to do too. Even tho we want to hang out gab and shop the kids may need some activities.
Decide if you want to do "games" ie gift swap,
seed or plant exchange, recipe exchange.
Will you eat pot luck/chuck wagon style at night? Restaurants?
Just think of it as a large housewarming party where people will need a place to stay over night.