Everyone: A camp chair, clothing appropriate for the weather and shoes appropriate for hiking, sunscreen, insect repellent, a flashlight, bottled water or other drinks, plates, cups, and eating utensils. 

Campers: A tent, sleeping bag / bedding, personal hygiene products, towel, washcloth, shampoo, soap or body wash, changes of clothes, etc.  Drinks and snacks.

Tent decorations: You might consider decorating your tent space. This can include banners, flags, solar lights, or other items of personal interest or that relate to groups / communities that you belong to.

Optional: Glow sticks, extra snacks, car chargers and backup battery packs for your phones and electronic devices, notebook and pen to take notes, and a drum or other percussion instrument for the drum circle.

Items for the Community Altar:  Items of personal significance to go on the community altar. 

Other:  Ritual garb, if you like.  Consider a costume / mask to wear to the Samhain Party.  Think nature deities and nature spirits - Faeries, Nymphs, Satyrs, Green Man, and so on.