Yes, I've done the math. Several times for both myself and others. (Evidence is on these boards

)
My recent catch-phrase is "Use a plan if it fits your dining, don't fit your dining to use a plan". It pretty much emcompasses the idea that if you dine the way the plans are designed, there's a very good chance of saving money. If you force your dining wants to fit the plan, then either you're going to spend more than you would, or just not have quite the experience you had intended.
The savings on the plans come when you use them as designed. Minimal sharing, minimal extras (e.g. apps on the DDP), and maximum credit usage. For the DDP as well, minimal 2TS experiences (DxDDP math is a bit different, because you get 3 times as many credits to potentially use at TS locations, thus making 2TS locations a bit more worthwhile, as well as including the appetizer).
Each plan has it's own "break-even point" and unless you utilized them as intended, you aren't going to reach that point.
For the OP's situation, it's tough to tell without knowing the number of nights the stay is for. Since most of the locations (except MM, which is being paid off the plan) are AYCEs, the little one will be free anyway (if you had a lot of menu service, the TiW may look better as you would probably buy at least a couple meals for the youngster.) Let's just assume 4 nights anyway though for sanity sake

. Also assuming that your dining habits will be the typical plan usage.
So, we have 4 nights of DDP for 2 Adults totalling: ($42 x 4) x 2 = $336.
4 CS meals @ roughly $14 ea = ($14 x 4) x 2 = $112
GG Dinner = $31 x 2 = $62
Boma Dinner = $31 x 2 = $62
LTT Dinner = $30 x 2 = $60
Adding the meals up and you get: $296
Add in snacks (avg $3): ($3 x 4) x 2 = $24
This totals $320. So you're $16 short of the "break-even" point. However, you still have 1 TS available (see the note above about using allotments

). If you're stuff right now without thinking about another TS restaurant, you will be better served paying OOP. If you want to add another TS, then DDP would pull ahead (and really, it could be any meal, even breakfast will pull it ahead).
Doh, the person who posted while I did reminded me about tax.
So, continuing from the above...
Add 6.5% tax (it's only 7% in Osceola County, where the All-Stars are located. Orange county is 6.5% where everything else is).
$320 * 1.065 = $340
So that changes it slightly, you'd save about $4 using the same plan with DDP. However, if you drop desserts from the CS locations (or heck, just drop it from one CS location

), this would more than make up for that $4.