If the criterion of Children’s Classic Concerts is to present a fun experience while opening a wee window onto classical music for those too young to reach that window themselves, then yesterday’s concert, launching the CC’s new season, did all that and some more. It’s not that uncommon for this kids’ staple to have them dancing in the aisles, but yesterday percussionist-presenter went one better, filling the front line of the stage with a flotilla of kids demonstrating their versatility at hilariously mimicking the faintly ridiculous sight of synchronized underwater swimming to Strauss’s Blue Danube Waltz, then persuading the entire audience to go in at the deep end by doing the same themselves.