Tonight with your 5 to 8 year old
The prompt
“If our family got a pet tomorrow, what should it be and why that one?”
What to listen for
Notice the "why" more than the animal itself, if they want a pet to cuddle and talk to, that points to wanting more companionship or someone (or something) that's always around and available. If they want a pet to train or take care of, that points to wanting more responsibility or a role of their own in the family.
If they pick something wildly impractical (a lion, a dragon), just enjoy the fantasy, it's not really about logistics, it's about the feeling of having something amazing that's theirs.
If they say "I don't know," ask what they'd want a pet to do with them specifically, sleep in their room, play outside, sit on their lap, the activity often reveals the real want.
What this tells you
The reason behind their pet choice often reveals whether they're craving companionship or craving a role of their own.