Leave them be - after all, you always sit alone at lunch.
Ask politely if they want to sit with you and your friends.
Sit down next to them and strike up conversation.
Bring your friends over to them and all eat together.
Dinner by candlelight and a movie.
Hiking followed by a picnic.
Cooking dinner together.
Playing board games and talking.
I don't like to travel
Mint Chocolate Chip
Chocolate Chip Cookie Dough
Get cotton candy
Ride the Ferris wheel
Play carnival games
You didn't go to the carnival
Girl Scouts or Boy Scouts
Any sports team
Mathletes or Science Club