School Fiesta Party

There is a very easy project called "papel Picado" which is kind of making a snow flake, but with colored tissue paper. You can also try making "el ojo de dios" or the eye of the God. Google these activities. Good luck.

How about having them decorate their own fiesta float out of a shoe box, tissue paper, stickers, markers, etc? They can then have their own fiesta parade in the classroom, through the halls or outside.

As for food, it depends on what the school and the district will allow. However, in the past I've done the following:
- play Mexican Bingo (loteria)
- make corn tortillas with the kids and cook them on an electric skillet
-cut out decorations (I can't remember what they are called but it's when you fold the paper into squares and then cut out shapes) then you can use it to decorate the room.
-play spanish fiesta music and maybe teach the kids a simple dance.
Good luck!

You could make a class pinata of the school mascot and hang it in the corner of the room for decoration?

Using shoe boxes or lids, they can make Fiesta floats decorated with flowers, ribbons and dolls or action figures. They could pull them around the room/table with ribbon ties.
Teacher or other adult could be the judge.

Using metallic garland or flowers and curling ribbons, girls can make "corona" wreaths to wear on their heads, guys can decorate "gold" crowns with stickers or jewels.

Face-painting is always enjoyed by children if you have help, smile...

Our kids would have a fiesta parade. They would dress in fiesta attire and we would provide balloons for them to carry. They would just march around the school and waive at the other classes. They also had a fiesta float decorating contest made out of a shoebox and decorated however they wanted. We did the mexican food as well.
Hope this helps!