First aid in a survival situation is paramount. Everyone in your group should have a basic knowledge of first aid skills and CPR. Thought should be given to your future community as well. Do you have someone in your group who is a doctor or who has an advanced medical knowledge?
Luckily basic first aid classes are available at a plethora of outlets. Often communities will sponsor CPR events and they definitely can be found at your local red cross. Another good source of classes is your local REI or outdoors store. Usually they have a wide variety of classes including: basic first aid, wilderness first aid, etc. For further knowledge, local colleges often offer Emergency Medical Technician (EMT) Classes in a semester of learning. This certifies you as an EMT but more importantly you will gain a lot of knowledge on how to triage a scene and start basic medical procedures to secure a patient. One of my favorite internet survival medicine resources is thesurvivaldoctor.com but there are a huge amount of sites out there offering all kinds of practical information on the subject. Go ahead and read, read, read but make sure you get some hands on practice as well. There is a big difference between learning and doing.