If it has a hard time retracting, is it worth taking a chance it won't retract (as it is designed) to instantly remove slack and lock on impact?
Especially for kids' sake, you might replace with new GM replacements or have a professional repair done.
This place is popular...
https://www.seatbeltplanet.com/p-35843-repair-service.html They are in the US. Maybe worth a phone call to see what your options are.
They can do different colors, if you want to jazz up the old ride with some crazy contrasting color.