You'll find Disneyland Guest Services in City Hall, just to the left of the main entrance, past the tunnel under the railroad track. No matter what you need, this is the place to go. They can cash a check, lend you an Assistive Listening Device or closed captioning activator, answer your questions, or wish you a happy birthday, and they'll try to help, no matter what you need.
The Lost and Found department is located outside the California Adventure entrance, to the left behind the wall. The Baby Care Center and First Aid Station are on the northeast end of Main Street, U.S.A. in the small side street between the Plaza Inn and the Main Street Photo Company.
Disney security is highly trained in dealing with lost-child situations. If a young child (under the age of ten) in your party gets lost in Disneyland, before you panic, seek help from security or report the missing child to any Disneyland cast member and follow their instructions. The missing kid is likely to end up in the same location as the Baby Care Center. Guests over ten years old who get separated from their group can leave a written message at City Hall.