There are many good cookie dough distributors around the country. I would look for one that had the products stored at their own warehouse and deliver in their own trucks. That way, they are in control and are not dependent on "common carriers" that can be very unreliable.
Another consideration is price. It looks like cookie dough is going to go the way of gift wrap and gifts--expensive! There is no need for cookie dough to have a retail price of $13-$15. It sold for $10 just a couple of years ago. I do not think the price of the dough jumped $3.00 to $4.00, just greed from the companies and our own groups. You think you are making more money but chances are your overall sales will go down as your customers rebel against ever higher prices (just like the gift wrap catalog sales!). I have heard of a number of companies around the country that will allow the school to set their own retail price. If you think $10 or $12 is high enough, then that will be your price. It sounds like a great concept.
Also remember that if you go the pre-formed cookie dough route, the cookie dough is made from a drier recipe. I personally like the tubs.
Final thing---Ask for references and call them. What was the service like after the sale? If you needed a few more items, could you get them, or did you have to jump through hoops and order full cases? How about prizes? Who pays? Good luck:)