I ride the SART frequently. Distracted, squirrelly kids–on bike and foot–are part of the landscape. Especially on Saturday. I love to see kids out there making their way to the beach. They are always riding with big grins on their faces. Of course, I'm an educator so I frequently deal with gaggles of 8-11-year-olds (try taking 300 kids on a field trip and being the one ultimately responsible for them). Sounds like you did great job. So what if a few roadies were inconvenienced.
That said my son's initial interest in cycling came by way of BMX. He raced and practiced at the old Coal Canyon track between Corona and Yorba Linda, the Orange Y track and others around So Cal. Being on a bike, making friends, training, racing, riding trails, et al was a great experience for him that has kept him into bikes. Over time and with a lull in between where he was focused on cars, this interest progressed into track cycling at the Velodrome in Carson and riding road (interestingly, he didn't ever transition to MTB). As a matter of fact I'll try to wake him up (some things never change) to see if he wants to ride as soon as I'm done watching Liege.
Whatever you can do to get kids out on bikes and encourage the healthy habit is good.