You can do car washes, spaghetti feeds or pancake breakfasts or gift wrapping during the holidays.
I would also list the specific activity you're doing and how it relates to Girl Scouting(IE, Help Send the Girl Scouts To The Living With The Land Tour At Disney World to Earn their Gardening Badge!, or whatever it may be) Because honestly if the fundraiser just said, Help Us Earn Money for A Disney World Trip, I wouldn't donate money or participate in that fundraiser. If it's just a vacation or trip for fun, I can think of more important places to donate my money or participate in fundraisers (and I know it may sound rude, but I'm not trying to be offensive, just being honest. With the economy in the state it's in, I just think people are more selective of who and why they're donating money too.)
Also, I would recommend to each parent that they try to sign up with one of the points websites that let you exchange those points for Disney Gift Cards (I use Sunshine Rewards but if you search this forum, there are other companies mentioned, I just can't think of them right now.) You can earn money by completing FREE surveys or you earn a certain percentage of your purchase when you shop with specific online retailers and then once you reach a certain dollar or point level, you can cash out the money for Disney gift cards. It may not seem like a whole lot, but if you have 20 families earn at least $50 (which is very reasonable) that's an extra $1000 for doing very little.