I know a lot of people like to put things in the bag that the guests can use while visiting, such as bottled water (with your own labels on them), snacks, lotion, sunscreen, candy, disposal cameras (those waterproof ones are great if guests go in the pool or water park) pretty basic stuff...I have heard of giving disney dollars if you have the money, but for eighty people that would get quite pricey. For kids I have heard putting inflatable beach balls for the pool, mickey ears, disney stickers and things like that. Also, check your local dollar store for goodies which will help you keep the cost down. Oh yeah and Target has a great dollar section with really really cute stuff and if you are lucky they have some stuff in the dollar section for half off so everything is 50 cents. In addition, I know people like to add guide maps of the parks & resorts, a list of things to see and do, and itineraries for the festivities,. And of course, dont forget to thank your guests

I hope this helps you out! Good luck!