I think the mixture of the 2 cereals give these treats a more magical look because the color looks more scattered, plus there were the little bits of cereal marshmallows that were a surprise treasure every so often. Plus, I feel like the fruit flavor from the Pebbles doesn't overpower as much as a recipe with only Fruity Pebbles would. If you want to take the mermaid theme over the top, you can sprinkle on little pearl sprinkles before the treats cool.
If you aren't able to see your grandchildren yet, like I am able to at this point, these Magical Marshmallow Treats are the perfect surprise to drop off at their door. They might soften in the heat, but will last pretty well and not spoil.
If you have a mermaid lover in your family, make them Magical Mermaid Treats. They will love you for it.