your 6 month could probably take them down but your 4.5 maybe pushing it. If I am worried about something I will make sure the insect is from eye to eye in length but usually they can take them down no problem if a little bigger. But better safe then sorry. Worms I don't go by that rule though
Both Cham's are about the same size despite the panther being 6 weeks older. I let one loose earlier and my Veiled ate it without any issues. It took him quite a few swallows to get it down fully but he didn't seem to be struggling with it. In fact he looked rather smug afterwards!