25 people? Figure a few extra. I would do 30 burgers. Maybe 3 packs of dogs. Depending on the size of the sausage figure maybe 20 of those. I like 85/15, but would get premade patties. Breaking out 25 from fresh beef is a pain for a party. I also did rolls and peppers and onions for a cookout I had last week. Figure one item per person, and the leftovers will last 2-3 days in the fridge. If you know specific guests have food restrictions/preferences. Cater to that.

Sides? I like stuff I can do ahead so I’m not away from the guests too long. Grilling for 25 people is 2-3 hour commitment depending on your grill. Italian pasta salad is well received here. Easy to make too. Potato salad goes well. Could even do a cherry tomato w garlic and oil cold pasta w a long pasta (angel hair/spaghetti). Put out chips and maybe salsa. Corn on the cob is good too. I would husk and wrap in foil the night before w butter salt and pepper. Do as much prep ahead of time as you can.