We used
DDP (once for CS and once the regular plan that includes a TS per night) when I took DS and a bunch of his friends (college graduation gift), and when I took my DD and two DGC (it's a much better value when you have kids under the age of 10 who actually eat!)...
The convenience factor is worth money! In the case of the college kids (who did want their sit-down meals!), the ability to "peel off" and not be w/me in order to get their meals paid for was invaluable! (Plus, they were very grateful for the treat and didn't skip ANY TS meals w/me--but they did peel off for almost all CS meals--also ok w/me as they had a TON more energy than I did (plus, I'm a
DVC/Disney vet so I don't "commando" anymore--and my DS' friends were all there for either the first or second time and they went from sun-up to the wee hours ("sleep is for sissies," they told me!)...
Anyway, they can count! (And my guess is so can your younger, responsible teens)...they knew exactly what they were entitled to and while one time one extra snack got used, there were lots of apologies and an immediate offer to either skip snack the next day or reimburse in cash--and they told me about it; I didn't monitor it in any way...just told them: "here's what you get; anything beyond what you get you pay for" -- side comment: they were all gung-ho to do the water parks until they found out that while I happily bought them 5-day park hoppers, I was NOT going to pay for an add'l 6 water park admissions; if they wanted to go to a water park, it was on them...amazing how the desire to go to a water park disappeared in less than a nanosecond!)...
The convenience of DDP when you're dealing w/kids you're "turning loose" makes it so worth it...you don't have to fret about whether they're choosing "expensive" food...and they can do all sorts of trading and planning--split a big CS (e.g., at Tangerine Cafe in Morrocco) in order to have an extra credit to use for Mexican food late at night--that was one thing my group of kids did)....they LOVED the independence the DDP gave them (and appreciated all the more the time they CHOSE to spend w/me)...
And while you can use the refillable mugs only at the resort, "free pop" will send one or more kids over to the drink refill stand quite frequently, I promise! My kids LOVED it...
The other trip we used CS was another time when the DDP QS plan works well--small children and one TS restaurant/day are NOT a good mix (at least not w/my small children!)...and it's pretty inexpensive for the under-10 set (mine DO eat!)...
Good luck w/your planning and decision...and I hope you have as much fun watching your kids have fun w/their friends as I did!