Make up a batch (or several) of pudding, according to the manufacturer's instructions. Get some of the relatively deep plastic or heavy-duty paper plates and pour a layer of pudding into the plates and then set them in the fridge. You'll need as many plates as you have students. Instruct your students to practice writing their name in cursive in the pudding before they can eat the pudding. They'll lick the pudding off their fingers, so you don't want them to share. You'll also want to have some hand wipes or paper towels and a hand sink on hand so that they can clean up when they're done.
Lay out a piece of parchment paper and write the desired cursive letters on it, or have the child write the letters, depending the child's abilities. Heat up some chocolate chips in the microwave or, if you need a particularly large batch of chocolate, you can melt it in a double boiler. Spoon the melted chocolate into a plastic piping bag or a plastic zip-top bag, and squish the chocolate down into one of the corners. Wrap a rubber band around the top to keep the chocolate from creeping back up and snip the very corner of the bag. Have the children trace their letters with the chocolate and then allow the letters to dry. The letters can be used for decorations on a cake or cookie or eaten by themselves.
Zen gardens can be made on a large or a small scale. A class project should be a larger area, maybe 10 feet by 10 feet square, although this depends on the number of children you have. You'll want to have an area lined with bricks or wood, and the sand in the center. For smaller individual zen gardens, give the children sand layered in a tray or cookie sheet. In the larger gardens, the children can try writing with sticks or they can use rakes to create more elaborate and beautiful cursive letters. Children can use their fingers to write in the smaller trays.
Put some shaving foam on their desks and have them smooth it all over the desk and then write in the surface. This is one of the least messy activities, and the shaving foam will actually clean the desk. This may be a good activity for after the pudding activity, to help clean some pudding gunk off the desks. You'll need several cans for a large classroom because the students will need lots of foam to really have fun with it.
Make sure you know about any food allergies before doing any of the food-based activities. Students who are lactose intolerant cannot eat pudding. Students with chocolate allergies clearly should not eat chocolate, but chocolate is also often processed in manufacturing plants that process both peanuts and tree nuts, which are some of the most common food allergies. The outdoor project can be lots of fun, but you need to carefully watch children with garden tools so that they don't become rambunctious. You can stick with the plastic tools they use for sandboxes to help prevent any injuries, and just be aware of which of your students are handling what tool. Also, if you frequently use an outdoor sand pit, you may want to come up with some kind of cover, as stray cats may use it as a litter box. In either case, you'll want everyone to wash their hands very thoroughly after working in it.