Do you need to subscribe to the ambulance in your state? Make sure you are JIC you need to call them because it might be better to call for help to come to you rather than birthing in the car!

What Misty said is a good idea and we had planned on doing that too if it was needed, but can you ask all of your neighbours (that you think are able to help) that you might need help and get their phone numbers so you can get someone to sit the kids while your help arrives. You might be surprised of how many would be willing to help and it doesn't matter what time of night because everyone gets excited about a new baby

Also be prepared that DH might not be able to be there JIC so the ambulance can take you but he stays home with the others.

Or maybe plan for an unplanned home birth