kjetjl is right,
free dining saves a BUNDLE and we have done it, but right now it's only available from 9/2/13-9/25/13. It means staying onsite, paying rack rate, and buying tickets from DIsney BUT you usually only have to buy a minimal number of days on the ticket (not sure if it'd be cheaper to do 2 days tickets through the room and 7 through
UT). I have noticed that when passes are bundled into a Disney room rate, the passes appear to be cheaper than buying from UT. Free dining is NOT available if you are staying in family suites at All Stars or Art of Animation, usually. Also, if you stay at a value resort "free dining" means two counter service meals and one snack per day, per person, plus a resort mug per person. Staying at a moderate and above gets you one counter service, one table service, and one snack per person, per day, plus a resort mug. Resort mugs are valuable as you can get "free" unlimited coffee, tea, iced tea, hot chocolate, and soda at your resort hotel food court (NOT in the parks). Kids under two can eat off your plate for free. Technically kids 9 and under have to order from the kids menu, regardless of dining plan. (I say technically because apparently there is some wiggle room here on cs meals, depending on location/cm.) Remember that you can pay for a Disney package over time (6 months? I think?) but within a certain window (45 days? 30?), you have to pay in full when you make the reservation. If you don't have the available cash to do that, it would let out going in september for free dining. However, you can roll the dice and make the reservation for early January, and hope they offer free dining! I am not sure what Disney's cancellation policies are. If you go in September, would your college student miss school for your entire vacation, or just a couple of days (i.e. come down for a long weekend?) If he's doing a long weekend, I'd suggest he take off either Thurs/Fri or Mon/Tues, rather than Fri/Mon, so he only misses one day of each kind of class (assuming his college classes follow the MWF or TTh schedule).
These are just random thoughts I have had; if I cannot plan my own Disney vacation, I like to live vicariously by planning vacation for others!! I think you need to do a pros/cons sheet for several different travel dates and see how they measure up.