The dining plans are worth it, so long as you already intend to dine according to them. They don't work so well when you try to dine outside their structure. Of course, that's very general and probably not very helpful

.
As far as "is it worth it to you?", that wholly depends on existing plans, dining habits, family makeup, and what you're seeking to get out of the trip. It's too tough to just say "Yes" or "No" because everyone's experience is different.
I've tried a few times to put it into general terms, but I can't quite convey it more clearly than "If you already plan to eat that way, then yes. Otherwise, maybe. (You'd have to run the numbers.)"
From the little information you've given, it does sound like you're a good candidate for one of the plans. CS lunchs and TS Dinners or Character meals are typically the way to go to best maximize the value you're getting for your credits.
There is a lot ot cover if you want the complete run down, so I'd suggest you poke on over to the official Disney World site and read up on the plans. It will cover a lot of the basic questions.
To quickly figure out if you'd save money or not, check out the menus for the locations you're planning and get a general estimate of what you'd pay at each place, paying attention to what you are entitled to for the plan. Add tax to that (since the
DDP covers that) and see if it's more or less than the plan would cost you. (You can see prices right on the DIS (
www.wdwinfo.com) under Dining->
Disney Dining Plan.)
After you've checked that stuff out, if you have more specific questions, let us know and we'll be glad to help

.