Teachers get so much stuff year after year that I always try to think of something that can be used right away. Gift cards are great, but I usually like to do something a little more personal. Here are a couple ideas for a group teacher gift. I did this when my kids were in daycare with multiple teachers caring for them, many I didn't know very well.
I once just took in bagels, different flavored tubs of cream cheese, OJ & coffee from Einstein. I arranged it nicely on a platter, provided holiday plates, cups & napkins, and then had my son make a sign/card to go along with it. Everyone really enjoyed the thought and of course the breakfast!
You could also do the same with a lunch from Panera, Subway etc. Or even make it on your own. Make sure you call the director and arrange a date to do this.
I have also taken in a big plate of cookies and eggnog for the teachers to enjoy throughout the week before Christmas. By just providing the holiday napkins & cups, it made it feel like a celebration.
Another time I purchased multiple copies of a paperback book I loved and gave each one with a bookmark my preschool daughter made. The bookmark is so fun & easy to make- cut cardstock paper to bookmark size, decorate it, laminate it, punch a hole in the top and loop a ribbon through it. The teachers all enjoyed reading the book and discussing it too!
Another time I did give gift cards. I purchased $10 gift cards from different places, wrapped them so they looked the same and put them all in one basket/gift bag. I included a note for each teacher to pick one and enjoy. They really had fun picking and see what everyone got. I think there was also a bit of trading too! Just makes it a little more fun.
Those are a few that I remember that the teachers enjoyed and appreciated. Good luck and have fun!