National Geographic Kids is an excellent resource for child-accessible information about eagles. Many zoo websites also have child and family-friendly information pages. The Cornell Lab of Ornithology All About Birds site is also appropriate, especially for older children.
National Geographic is a trusted source of scientific and cultural information, and its kids' pages are an excellent source of information for young learners as well as teachers. The information is simple but accurate, and the format is attractive and child-friendly. National Geographic also includes graphics and range maps. However, the only species with in-depth information on this site is the bald eagle.
The Association of Zoos and Aquariums as well as many individual zoo sites, such as the San Diego Zoo, have family-friendly information pages. These have a similar presentation as National Geographic but tend to focus on the eagle species that exist at that particular zoo.
Cornell University's Lab of Ornithology maintains the All About Birds website, focusing on North American bird species. For eagles, specifically, this is a good resource for information on bald and golden eagles. This is particularly accessible for older children, or young children with help from an adult. All About Birds contains similar types of information to National Geographic but more expansive and in-depth with measurements, life history statistics, conservations status and even sound clips.