Vacation Question!! Disney?

My girl scout troop is planning to take a trip to Disney. We are a group of about 14 girls (15 years old) and 4 or 5 adults. We need to find a cheap, yet comfortable place to stay. If you could give me an idea of the best time to go (preferably this summer), the best airfare, the best place to stay with prices, or any other ideas you have and may be familiar with. I appreciate your help!