Children can stop by the Hopkinton Public Library and sign up for the “Dream Big Read!” program starting Monday. Denise Kofron, the youth services librarian, said summer is her busiest time of year, and she encourages even toddlers who can’t yet read to get involved in the program. “I say to those children, ‘Just have someone help you keep track of the hours your mom or someone is reading to you,’ ” she said. Children up to sixth grade can get a reading log at the library, and use it to keep track of the time spent reading or listening to audio books. For each hour logged, readers will earn one “Library Buck” to spend at the library store starting on July 9. Similar summer reading programs are taking place at libraries across the state in an effort sponsored by the Boston Bruins, the Massachusetts Board of Library Commissioners, and the Massachusetts Library System.