Congratulations on the job, and the degree completion!
Kids at that age really need grounding, and love. Even while you teach them information, they need to know that they belong somewhere, and that their voice is heard, and that they need to care for others.
They are young to be learning concepts of teamwork, but I think it would be great for classrooms to teach how to stand up for each other. Some of that is included in new anti-bullying incentives, but it's also important to reinforce the positive -- that school friends can not just hold each other accountable, but link with each other.
(A few teachers have introduced wonderful wikis with older kids, where a topic is presented and everyone takes off with informal input.)
Back to preschool -- a teacher prepares students for the next step. Once in mandatory schooling, they will begin to have tests much earlier than it seems they should (some classes test 26 days per year!), and school will start to look scary. It's important that kids learn to love school, so they will be eager to learn, and do not drop out later in life.
Big concepts for little humans... but it might just take one or two conversations for it to stick.
Sing a lot of songs, give them roles to help out, let them rest quietly, let them eat when they need to.
Young kids seem to have shorter schedules for low blood sugar, tiredness, and tolerating chaos. Listen to the cues and see them as physical needs-- resisting the temptation to just get angry and view crankiness as bad motives.