In that situation, I might have assumed that the side table was set aside so most of the kids could find the things they liked without having to ask a lot of questions about "what's that thing?" and "Dad, would I like this?" (and a parent who knows their child would rather have something from the grownup side can serve it), rather than being intended as "kids only." As a host, I might do that if there were spicy things on the main buffet, for example. It's a bit like putting the bowl of plain fruit punch where everyone can reach it, and the alcoholic one out of reach of children. But if I wanted to give the kids priority, I would do so explicitly (and probably let everyone have a chance at the macaroni and cheese once all the children had taken a plate).