As a more portable and budget-friendly alternative, consider a small emulation console. I’m very happy with my ANBERNIC RG35XXSP. Since the screen folds like on the original GBA SP, it’s absolutely tiny and fits into any pocket - without having to worry that the screen might scratch. Configure it correctly and you can close the screen to suspend games.

This kind of system would also make for a great first gaming device once your kid is around five years old.