I also had a child with a peanut/tree nut allergy in care for a few years and I cook most things from scratch but I really had to read labels on crackers and any food I bought in packages. I had to carry an epipen around everywhere we went which was kind of scary but she never needed it thank goodness. All the other daycare children watched out for nutshells for her because people feed them to the squirrels at our park.
For almost 4 years I've carried around the puffer for my little girl with mild asthma. I count my lucky stars that we've never had any incidents, but I know for sure that both of my dcMoms were great and if we ever had an emergency that they would be here FAST. I think that's really important. If you have a child with any chronic illness or allergy make sure the parents work close to you and can get there at the drop of a hat to take the responsibility off your hands and take care of their sick child.
We probably all have the same arrangement in place that we tell parents that if we ever have to call 911 and send a sick child to the hospital they will be responsible to meet them there. We can't leave the other children. Make sure you have a clear policy like that in place.