I’m leaning towards setting that one up with a mushroom or something to start.Welcome to R2R. Love the idea of toddler tanks/jars. Great to get them interested. Lots of knowledgeable and helpful people here who will support and advise you when needed.
I’m thinking supervised feedings of pellets would make for a fun and manageable interaction for a toddler. Just have to make sure I find a mushroom with good feeding response.
I welcome other ideas for tank inhabitants. Runner up is currently a rock flower anemone.