My daughter is getting ready to turn 3 - she goes on playdates and birthday parties all the time.  right now, we are at the stage that the parents are still included so not a worry yet.  At preschool however, we do  not leave her injectable with her but they know the signs they are to look out for and I am usually about 10 minutes away and the hospital is about 5 minutes from her preschool.   We did make sure to emphasize the need for urgency in case of emergency and include a "to do / FYI" for the EMT’s that respond or to give to the ER staff in case they get there before we do.   We are very fortunate that the people in her preschool take her condition in stride just as they do with any other condition like bee allergies or diabetes. . .they really appreciate that she is a little girl that just happens to also have this condition rather than focusing on the condition itself.