SPD vs. FD with DxDP

[inkedupmomma]

Can anyone explain to me exactly how the SPD deal works? I know every one has said that its dining and tix at kids prices, but when I did the math last trip (January 2013) it seemed like a straight up 20% off our package. We do upgrade to the DxDP. Can someone explain exactly how it will work for us? We are going again in January(16-27), a party of 5. 3 adults, 1 child, 1 infant. POFQ, DxDP, and 10 day PH Tix. I believe in the past Free Dining has been a better deal for us, but I'm not sure... I'm 37 weeks pregnant and baby brain is not allowing me to do any math right now! lol!

Thanks guys!