We used to order Timbercreek as well, since they offered a small percentage of sales to our preschool. We used to get monthly deliveries, but stopped, primarily because of the 1am delivery time, and also because they stopped the fundraising partnership. (I do miss the way their box would force me to cook creatively)
If I could add my .02, partnering with local schools as a fundraiser, similar to what "Market Days" does might be a way to increase your business. This would reduce your delivery cost - and maybe I could get the smaller boxes less often. I don't eat organic exclusively, so $35.00 worth of veggies twice a month would eat up a lot of my food budget, but I'd definitely be in the market for a monthly pick-up at my school.
The trick would be finding schools that have an active enough volunteer base to do the work of handing stuff out.