I'm not a parent, but I am a lawyer, which means I always have an opinion.
1) Try finding other parents in your area you can trust, and make mutual arrangements with them for emergency child care, especially emergency contact numbers.
2) If you have one, talk to your religious advisor about services available through your congregation.
3) As 2, above, check with your local government to see what kind of services are offered by the city and/or state. What you find out may either relax you or galvanize you to action. I have heard but cannot confirm that some school counselors are particularly knowledgable.
4) If the only people you trust with your kids are out-of-towners & you can afford it, find a way to get them some kind of method to either get the kids to them or bring them to the kids- some kind of pre-bought plane/train tickets, or some kind of emergency credit/debit card ($1K limit or so) that is never used...
5) Make a will. Plan your estate. Make sure the trustees/executors/guardians are all people or institutions you trust. Reexamine your plan every 5 years, and every time there is a major life changing event (death, divorce, adoption, lottery, etc.) in your immediate family.
6) Give your kids little (playing card sized) laminated cards they can carry that have contact numbers for anyone and everyone you think should be notified in case of emergencies. I know it sounds obvious, but include all of
your contact info as well!