I'm concerned about this too. Last trip DD was under 3yo, so we could feed her pretty much anything from our adult entrees or the buffet line (at no cost). We got her a 'kids meal' only once when we both wanted entrees she wouldn't have liked or couldn't have due to food allergies.
Next trip, we have to pay for her on the plan...and almost all the kids menu items are identical- ugh! I know kids like routine.... but 2 weeks of chicken nuggets is cruel and unusual punishment! I keep telling myself 'it's less than $20/day' but she could make a lot of different choices for that $20. And my own personal irritation- WDW chefs do SOOOOO much to accomodate food allergies, and PB&J is the go-to on many of the kids menus? So she gets 1/3 less choices because she can't have nuts? We'll be spending a lot of time at the MK QS with the "snack" brocolli and cous cous on the days we don't have buffets lined up. (Awesome thread on DDP snacks BTW) Yogurt for protein I guess- because she will NOT be willing to eat the same food every day.
Disney really needs to improve their 'kids menu's (best improvement- vary them, not every restaurant needs to mimic McD's) or let you opt your child out of the dining plan and go OOP for them while using the DDP for the adults. I know we parents have a bad image nowadays- but not all of us feed our kids 100% junk. My kid expects vegetables and a variety of main dishes, even at 3yo. (and at 3yo- no one should have to be in the restaurant with us if I'm having to try to convince her to eat chix nug or mac&cheese AGAIN. Are earplugs part of the DDP?)