Okay, I shouldn’t answer this, because I spend plenty of time creating art, and there are no species clamoring for my attention (currently working on some crows.) But I would very much like to encourage you, and have a few thoughts:
Watercolor is a difficult medium to work with, although it can look effortless. For example, with watercolors you can only get white by leaving the paper blank, which can be tricky (although to some extent you can add white by using gouache, which is just opaque watercolor)
Because watercolor is transparent, you can’t just paint over mistakes. Other paints, like acrylic or tempera, are more forgiving and easier to correct.
If you don’t feel you have the manual dexterity to render tiny details of tiny organisms in a tiny format, go large scale. If you make your images bigger, you can use bigger brushes and bigger stokes, and still show the level of detail you want. Or use larger needles, heavier threads, and bigger stitches, if you want to try embroidery.
I bet you already draw or paint with your son, and I imagine you have more dexterity than you think you do. So use whatever materials you already have on hand, like colored pencils or even crayons. We all know how to use pencils, even if we are not comfortable with a brush or needle in our hands. A pencil or crayon drawing could be satisfying on its own, or could become the basis for an embroidery or painting.
Finally, just try it. If you don’t like what you make, try again, as long as you enjoyed the process. Many artists are process-driven, and care less about the product, than about the act of making. Go ahead and make that butterfly, that flower!
Here’s another thread about nature art:
https://forum.inaturalist.org/t/for-those-of-you-who-are-visual-artists-do-you-like-to-draw-paint-anything-from-nature/33808