Electric Shock at 5V and 40 A
Your 5 V is far underneath the standard hazardous voltage levels (50 Vac, 120 VDC) and far below anything that can cause harm.

This low voltage is insufficient to push a harmful current through dry skin. So if that's their only point of contact, you're OK.

However, it depends where you're planning to deploy this as to how far you have to insulate it and protect from contact. 5 V @ 25 A is more than enough to hurt the user if they put the wires in their mouth. Consider this if, for instance, the wires on your lights are accessible to a baby crawling on the floor, such as with decorative lights.