No. In the event that your child makes it to guest relations they may check the magicband to find your contact information (through the resort reservation) but it is a last resort option. Children under 7 default to baby care center so they can not check there.
If your are worried about your child getting lost either print out and laminate a card with your information or get the tattoos with your information. You can also write your cell number on the inside or outside of the magic band in sharpie and then seal it with clear nail polish or liquid bandage. Then just have your child know to tell the CM where the number is.
99% of the time children are reunited before it even gets to calling the parents.
only if they have access to that information. A cm working concessions probably does not. As far as I know there haven't been reports of cm using magic bands this way. I would us temporary tattoos or other identification tags to provide that information. Also, CM cannot remove or look in clothing so don't stick it in the child's shirt or shoe expecting it will be found.