If this is one or two children, I would call the parents and ask what is safe. My daughter has allergies and I know I would love for someone to be so concerned as to ask. I'm not sure who you asked, so that is why I suggested that. If it's 6 different kids, then try the following:
Try whole, organic foods. I recommend organic for lots of reasons, but in this case, the labels will be clearer and ingredients should be easier to understand.
Small boxes of raisins- but do read the labels to make sure about the oil. Usually these are safe.
Apples, oranges or clementines, bananas. Organic no-sugar-added fruit cups might work- applesauce, peaches, mandarin oranges, etc.
Baby carrots or other cut-up veggies in bags. Read the bags to make sure it is only the veggie in the bag and nothing else.
Trader Joe's has bags of freeze-dried fruit (bananas, etc) that is crunchy and has only 1-2 ingredients and might work.
Try brands that specifically cater to allergies. Stores like Soup To Nuts or other health-food markets can help too. (There is a fantastic one in Winfield called Nutrition Network.) If there is nothing like this around you, try the gluten-free, sugar-free, or raw/vegan section of the grocery store. Usually there are brands there that are marked for multiple food allergies. "Enjoy Life" is a brand of snacks that might be safe, and "Yummy Earth" candy and lollipops would probably work for you. There is an M&M type candy called SunDrops that might work. (Regular candy is going to be contaminated with peanuts and probably soy.)
Hopefully, this gives you a start. Obviously, you could make your own items to take, but I know most schools won't allow that these days, so I tried to stick with store-bought items.