There are lots of cooking things you can do without much in the way of cooking utensils/methods, but you may need to think outside the box a little. I used to work at a school that held big school dinners every Thanksgiving/Christmas/Easter and every class was required to contribute a dish to the meal (and you had to do something different for each one, no repeating the same thing), but we couldn't use a stove etc, and could use an oven only if we took it home and baked it there.
One thing I used to make with my class was this: www.kraftcanada.com/recipes/cool-n-easy-mousse-pie-107197 The grocery stores here carry pre-made graham crusts, and I would buy those so that the recipe required no cooking, just refridgeration. It was easy enough to bring in my kettle from home for the day to boil the water, and my hand-held electric mixer. You do need a VERY large bowl though, as the mixture splashes a bit when you first start the mixer. It calls for strawberry jello, but any flavour works. Grape was always popular with the kids. I still make it once in a while for myself, though I prefer to make it with lemon or lime.
Depending on your school policy (I know some schools here have banned candy in any form at any time, which I think is completely silly. they should allow it on holidays/special occasions so that children learn it is not "bad", but that it is to be eaten once in a while in moderation as a treat.), there are all kinds of "cooking" things out there for all kinds of holidays, "building" things out of candies for holidays. Just hit up pinterest. Like these Chrstimas trees, needing nothing but a tube of pre-made icing and some peanut butter cups. www.simply-blessed.com/peanut-butter-cup-christmas-trees-2/
WIP Elegant Irises by Amanda Butler Lazy Days by Mystic Stitch pg 1/24 (BAP) Nativity Story Table Topper pg 1/6 by Blackberry Lane Designs (BAP) Amazing Grace by MBT (BAP) pg 1/6 Baby Ark Sampler by Bothy Threads pg 1/4 Skate by AAN Herbes et Epices by Madame La Fee Ornaments 1/12
Completed 2020 Names of God by MBT Ponchos x3 (2 nieces, 1 doll version!) Christmas ornaments - 11/11 Soffia by AAN