Here's your secret weapon, in case you haven't figured it out already: you have an army of adorable kids on your side. This gives you such an unfair advantage, it's unbelievable. Obviously you won't expect the kids to go out and do their elementary school fundraising on their own, but you should definitely base the fundraiser around them, and get them involved in a very strong way. This will have two positive effects - for one, your profits will soar (come on, who won't buy something from cute kids to help out their school?), but also the children themselves will learn a valuable lesson about how teamwork can help them reach some pretty important goals.
It helps if you choose an elementary school fundraiser that fits well with your group. Do you have enough people that you don't really need to worry about minimum order requirements? If that's the case, maybe a catalogue fundraiser would be right for you. On the other hand, if your group is on the small side, a direct sale item with high profits might work better for your team as an elementary school fundraiser, and you might want to consider something like candy bars or scratch cards for that. If the kids can get permission to sell candy bars to their fellow students as well, that could an outstanding elementary school fundraiser.