Ages 5-8.    When third grader and inventor extraordinaire Ada Lace learns her teachers are in dire need of new school supplies, she's eager to lend a helping hand--but how? With a bake sale? A class carnival? Most ideas seem out of reach for a kid like her, until Tycho suggests Ada try her hand at posting informational videos. If she's able to build up a big online viewership, she could easily raise funds for their school. And with Nina as her visionary director, Milton as her comedic cohost, and Ada as the scientist star, making fun videos will be a piece of cake! Or so they think.      128 pages hc