A drawing too difficult to understand for a 7-8-year-old kid?

(Go to picture 6 to see the material used)

One of my colleagues is leaving the company. He asked me if I could draw something for his son who is into robots and science in general, so I decided to draw a little story of 2 little cats, a chick and a duck teaming up to rescue their companion from a fire-breathing dragon 🐉 🔥

I showed the drawing (before it was colored, cf. picture 5) to another colleague who told me that she didn't understand the story at first because there were a lot of elements. I'm scared that the son may not understand, he is around 7-8 years old.

Do you think the story is too difficult for a 7-year-old kid to understand? Thank you for your honesty 🙏