Gosh, I can certainly identify. It sounds like a fun and pleasant work environment, and I bet you'd really enjoy it!
I went back to work after my daughter was nearly grown, into my field of teaching, and had severe anxiety when presenting myself and working as a substitute until I was hired full-time. My insecureties made me "overly" conscientious at first, but eventually I learned to relax and go with the flow. It's no big deal, ya know, and one shouldn't feel so anxious. It took me a long time to understand that.
I hope you will turn in your application, go to the interview with bright and shining confidence, holding your head high as you show them what a wonderful employee you will be.
Good thoughts,
Seeker