When my families did reunions when I was younger, they did option 3 with modifications. Each nf brought a meat and two sides to share with everyone. You brought enough to feed 12. Everyone pitched in money and ice cream was served in the afternoon in the summer or a cake/ice cream was served if inside during cooler months. It worked well and noone went hungry. Everyone brought their own drinks.
Now, our reunions work like this--you make a reservation for x number of people and send in $Y for each person. Organizers can either cater meal (or on one side they make it themselves.) Very simple and easy; we just show up. However, if you are having this in a conservation area, probably wouldn't work.
Or, do a combination of the above--have each family contribute so much money and buy meats to grlll, buns, condiments, and have families bring sides and dessert/snacks to share and their own drinks.
Entertainment: someone set up horseshoes, others brought balls, bats, etc. Someone would say "let's play whiffle ball" and a game would start. Same for other games. So, just set up the equipment and get someone to start a game. Others will just want to sit around and talk.
As to your options:
The trouble with option 1 and 2 might be that nf or foo wouldn't mingle as much. I'm not sure people will go to other people's tables and ask for their food.
I would go with an option 3 potluck with modifications---don't assign categories. Keep it simple with something like:
We will be having a potluck meal at noon.
Each family should bring the following to share:
Dessert or snack
Each dish should feed at least 12--remember to bring serving utensils!
Bring your own drinks and table service/silverware, chairs, and umbrellas.
Remember swimsuits and towels for the pool.
Bring outdoor games, as well as some toys for the kids.
This doesn't require much organization at all, other than making sure you have enough tables to put the food on, extra napkins and throw away serving utensils. Maybe some paper plates and forks in case someone forgets.
Our reunions were well over 100 people. Have also done the above with Boy Scouts, sports teams, church (all large numbers.) It works out great.