I would talk to the room moms for each of your children's classes. They'll be able to give you the best info.
When my kids were in MDO, they always did group gifts from the class - that way, if everyone pitches in $5-7, the teacher gets a nice $100 gift.
In elementary, some of the classes have done group gifts, some have not. However, most of the time, each classroom in a grade adopts a specials teacher. For example, if there are 5 second grade classes, one would be designated for PE, one for music, etc. Then the did a group gift from the class. Sometimes, that's a monetary donation, sometimes they simply ask everyone to contribute something along a theme, and then make a basket (ie last year, they did a snack basket with diet cokes, candies, chips - specific types specified by the teachers at the beginning of the year.
That's another point... In the two schools that my children have attended, the teachers all fill out a one-page form at the beginning of the year with their likes, dislikes, allergies, etc. Everything from their favorite candy or drink, to their favorite restaurant or retail shop (that way, room moms know how to spend the $100 as well).
I would definitely talk to the room mom before you shop. Many don't make the announcement of a group gift until after Thanksgiving - I found this out the hard way one year!
Good luck!
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