Look at various companies/businesses in your community and talk to them to see what they offer. Many, many companies have a person who can help with items like this.
For example, Wal-Mart will match up to $250 whatever funds you make in a car wash. Get on their calendar, make $250 and it'll double. It may be more in your area but you'd have to research it.
Kohls, Target, and other retailers have their own programs. Target allows you to fill out a short form asking for something and they review the applications monthly. My experience has been that if you ask for $40-$50 worth of items or on a gift card, that you'll generally get it. If you have multiple stores for a particular chain in your area, apply at each of them. Each store is independent.
You can use the cards to raffle off or to buy stuff for the trip etc.
Car washes can work but it does take planning. Arranging for a Wal-Mart parking lot make take a few months scheduling with the store. If you have enough people to make a few hundred bucks, it's easily doubled. Getting on the calendar for a few different stores, can easily help you generate over $1,000 or more.