Garden. This is a more simple, classy choice. Cover the tables in white table clothes and place vases of flowers on each of the tables.
Hollywood. Decorate with glitz and glam using black silver and gold as the main color theme. Display cut out stars featuring each of the family attending.
Fiesta. This is a great idea for a family dinner. Chips and salsa, bean dip, pork salads, taco soup, really the options are many and a crowd pleaser.
Around the World. This would be a fantastic theme for your meals. Serve Hawaiian one meal and Mexican the next. Maybe even celebrate with food options specific to where your ancestors are from.
Western. Celebrate with good ole’ BBQ and a western hoe down. Serve finger friendly food and maybe offer some country dancing! Photo Source: Design Dazzle 
Glow in the Dark. Grab oodles of glow sticks for everyone to wear. Play games using light up balls and display a disco ball.
I like your family reunion shirt ideas you put on the sixth slide. I really like the first design because, like you said, everything is contained and it looks clean. My husband and I are planning our family reunion this year, and we’ve been thinking that it would be fun to make shirts for everyone. Maybe we could do a design similar to the circle one for a crisp look.