Every time my son who is 6 is with me he wants to keep the fish to look at it longer. Of course we can't do that we let it go quickly so it can live on. I saw online where some guy had built a custom "viewing box" to look at the trout he catches before releasing them and that gave me the idea to get one of these:
It collapses down real small and light and most of the small trout in the Smokies would fit in it fine. I figured I could put a trout in it and we could look at it for a minute or two before releasing it. I think that would be enjoyable and fun for him. Of course temporarily holding a trout against it's will may be against some regulation. If so then I will ignore that regulation.
One of those squishy bowls might work too. I think the trick is to not stress the fish too much aka just keep it captive for a minute or two which is quite a long time when you consider how brief most c & r events are but still not long enough to probably cause any harm to it.